i dont really understand why people put one player at starter at 1 position and backup at another - almost any time they play, they should be playing that starting position anyway. not necessarily... but thats usually going to be the case. and further, if a guy is better at one position, may as well have him play that position! i would keep your starting bigs at their spot and thats it - ill sometimes toss them as #4 for the other big spot or small forward in case of extreme foul trouble. i find that doing what you are describing either doesnt work as intended, well thats usually the case, but it may also sort of work as intended but you get these poor substitution patterns where guys are subbing out after they get too fatigued, and end up getting subbed in not rested, basically hurting their performance for the rest of the game - just to get a couple extra minutes early.
i do go to the point of having #3 guards and bigs, sometimes even a #3 2/3 or 3/4, and the rotation there *still* is not intuitive and sometimes can even be detrimental. if you have unbalanced stamina in the starters that goes a long way to make a 3 way rotation effective. but in general i am a fan of using a guy as #2 at 2 positions when appropriate - i used to always do it, as your #3 big (for example) is almost always better than #4. but there are detrimental effects on the way substitutions and fatigue will play out - so i no longer always do it - only when there is a compelling reason to do so. in your question, the starting PF is enough to get him his minutes - you dont really want to push him past the appropriate fatigue level just to get a couple extra minutes. its a tough balance - when guys are way better, its worth them fatiguing more to replace ****** guys. but a guy who goes from say 23 to 26 minutes often just ends up getting those 3 minutes early and then spends the whole game fatigued. it just doesnt really work out as you'd hope - it doesnt distribute those 3 minutes evenly throughout the game, or even put them at the end, which would be way, way better.
with martz, its not surprising he is struggling. the problem with lp and per scoring is its like, it sort of seems to use one or the other, and if you arent really good at either, having some skills in both doesnt get you far. when you are great at one, the second area seems to chip in... sometimes... it depends. for like 90 ath/lp bigs that 50 per vs 1 per definitely helps. but for guys with so-so per and lp scoring (make sure to include ath/spd - a 90 ath/spd guard with 40 per definitely benefits from 40 vs 1 lp, but hes already an able scorer without the lp), im not sure it really helps much. martz's problem is if you take away the per, he is mediocre on offense, so i dont think it does very much to help him. some yes, but not that much.
again on the morgan at backup pg question - what are you going for? it sounds like you are envisioning a depth chart, lets just consider the big 3 guards, like this: pg - grotberg, morgan, knight, sg - morgan, grotberg, knight. whats that buy you? there are basically 3 options to consider. 1) grotberg and morgan are fresh enoguh to play - then it goes grotberg morgan. 2) grotberg is fresh, morgan is not, knight is - then you have grotberg knight. 3) grotberg is tired, morgan and knight are fresh - then you have knight morgan (the sum of the position rankings for knight morgan is 3 + 1 = 4, the sum for morgan knight is 2 + 3 = 5, so it would always be knight morgan). theres really no difference between that and grotberg knight and morgan knight - except that the sim is now "confused" and will substitute irregularly, which is almost never something that works in your favor. now, there might be the result that knight plays a bit less - probably a bad thing, considering the drop off is not that huge (see comment about the couple extra minutes costing you all game, especially with grotberg on getting tired). ive tried and tried to use these kinds of depth chart manipulations to result in a more favorable sub pattern, and gave up - and that was when i didnt let ANYTHING go, no advantage was too small, id spend months searching for a 0.1ppg advantage or something that gave me 0.1% better chance of beating a tough opponent. so id really just stick wit the basic rotation there.
now, if you were to say, my goal is to have grotberg or morgan play pg, and knight only play sg - that can be done. you do pg - grotberg morgan space knight, sg, morgan knight. now when grotberg is tired, and morgan and knight will be playing the 2 guard spots, the morgan knight setup is 2 + 2 = 4, while knight morgan is 4 + 1 = 5. so morgan would slide to PG in that situation. at times, THAT kind of depth chart manipulation can be incredibly valuable. note the difference - this manipulation has the clear and tangible advantage of adjusting who plays where (when your 3rd player favors one position). the kind you seem to be asking is going for the unclear and intangible advantage of maybe my backups will play less, which often is not the case at all, and when it is, its usually because the sim engine subs irregularly which is almost always bad. rule of thumb, if you have a clear and compelling reason for this stuff, go for it. if not, stick with the simpler depth chart setup (but almost always go to 4 deep).
for padillo v francis, IMO, the difference is not big enough to warrant a 3rd and 4th big setup. id just play one at #2 at one and #3 at the other, and visa versa (in case of foul trouble with one of your core 4 big men).
as far as backup sf goes, its sort of hard to go wrong. you can play any of your 3 backup players (including that guard hatton or whatever) and its probably fine, they looked about the same to me when i looked, which is why i said just do whatever (although there probably is a best answer). or, you can use one or both of your backup bigs as backup sf too. lets see... wow, lymon and martz have REALLY good stamina, and francis and paddillo are up there too. thats a really good situation stamina wise. id definitely use one of them at sf backup, padillo i guess. he is WAY better than rodriguez.
on that last note, you may want to use francis as 2nd at the 4 and 5, with padillo as 2nd 3 and 3rd 4 and 5. it would keep those 3 ****** guys from getting minutes, which is good, but you have to be careful to watch the impact on fatigue of the other core players. with the stamina of your 4 bigs so good, you could probably afford to do that, i would guess.