I'd like to get some opinions about and success when, using R & LH Specialist.

They are very much underutilized.

I tried to use LH specialist.

The guy seemed perfect for that role, 45 durability 5 stamina he should come in for one lefty then leave. Instead he pitched 18 times for 6 IP on the season.

When I used a LSP he pitched about 1 inning per month.  Waste of a roster spot imo.

Thinking out loud:

Once a pitcher is in that grey area between his TPC and MPC, that's when the pull rating really comes into play.  If you have a specialist available in the pen, and the engine can make a determination that the specialist is a better option than the current pitcher for the next pitcher/batter match-up, then it adjusts the pitcher's pull rating up by one.  So a pull rating of 1 gets treated like a 2, a 2 like a 3, etc.  In essence, the presence of a quality specialist creates a slightly quicker hook for the engine to change pitchers than would be the case if there were no available specialists in the bullpen.

"Specialist is not as good (in an overall sense) as Setup A, or he'd be one."

This excludes the situation in which the Specialist is a short STA/DUR guy who favors one hand.  Although you could make him a Setup A and pull him after one/two hitters, regardless of handedness, I'd prefer to have the sim try to seek out matchup opportunities for him, especially in situations with runners on.     

It seems like it wouldn't be that tough to code using a combination of tpc/mpc, pull ratings, the oppossing batter, the inning of the game, and the current game situation.

It gets to the 7th and the engine starts to recognize that its time to think about pulling the starter.  Its a tied game, it looks at the batter at the plate.  Is he a lefty?  OK, you're starters pull rating is high (lets say 4) so the engine decides its time to pull him.  He first checks for a a LHS specialist that is available in the 7th.  If he's there, the engine calls on him.  After that at bat, the engine looks again at the next batter.  Is this guy a righty?  Does the LHS have a high pull count (lets say 4 again)?  Then he automatically gets pulled for either a RHS or a setup/A.  However, lets say the batter is a lefty, now the engine looks at his pitch count to decide if he needs to be pulled.  Lets say he's pitched 6 pitches.  His pitch count settings are 5/5; he's automatically pulled.  However, if his pitch count settings are 5/15, the engine lets him stay for one more batter and the game continues forward.

I've seen others allude to there being a way to setup your bullpen so that a LHS will work.  I kind of think this is possible, but I think it in order for it to work like you envision, we'd have to setup our bullpen in a way that few of us do.  How many put our best reliever as a setup/A guy, available to come in during the 7th and pitch an inning or two w/ a low pull count?  Something like that would preclude using a specialist.

Awhile back I picked up two specs, both with over 80 against their respective H's. About the 3rd game after I started using them, the sim inserted my next starter in the 12th to close and left both those guys on the bench.  I immediately demoted them. Guess I need to see if simmy considers handedness of the batter when choosing the RP?.

I used to use specialists but after the frustration of them never being used I have pretty much given up.  If the guy is good enough to make him setup B, then do that, or else hold him in AAA and get a different guy.

A couple of possible exceptions:
* A minor league callup to replace an injured RP could be a specialist for 1 or 2 weeks he's with you.  In this scenario you are probably hoping the guy doesn't pitch because he's not a ML quality player but you'd rather have that extra pitcher just in case.
* If your bullpen is completely stacked, you have multiple guys who are All-Star caliber and one average guy.  Make the average guy the specialist because you don't want him in there often, you'd rather have the other guys who are really good.
* In the playoffs you might demote you Setup B to a specialist, so that he doesn't pitch as often.  When I'm in the playoffs I go to a 3-man rotation and do this:
     SP4 --> SuA
     SP5 --> LRA
     LRA --> LRB
     Worst SuA --> SuB
     Then I'd drop my SuB and add an extra hitter to my playoff roster. 
* I'd be more likely to use a RHS than a LHS, especially if it also fulfills one of the other 3 exceptions above.

Has anyone ever tried LHS/RHS instead of SU/CL? 

Seems like you could "force" the engine to make decisions you want to make.     Of course, if you've got a couple of lights out guys, you probably don't want to limit them to LHS/RHS.

I have a LHS who has made 7 appearances in the first 22 games of the season. I may have had him as SuA a couple times, but I think the main thing is that he is the only lefty in my bullpen.

I use the specialists but mainly as a backup to the setup pitchers. When my two setup pitchers are 100% , I have a RH & LH specialist set for 7th inning, pull rating 3 and 15/15 pitches then switch them to setup A & B when the main pitchers need a rest. This pitcher is right for the specialist role .....

Hardball Dynasty – Fantasy Baseball Sim Games - Player Profile: Gene Breen

I would just code it simple, like 7th inning or later, when the sim is going to go to a reliever, any reliever, lob the specialist in there against the appropriate hitter, get that out and then bring in whichever RP was slated next.  Let's face it, no one is going to carry a specialist on their roster unless he is special against, say, a left handed hitter only.  So he should be pretty lights out against that one type of hitter.  Give him his 5 pitches a night and get him out of there.  

Looking into it, I might now understand why it seems like they're under-utilized... The site says that Specialists come in to get the opposing team's best hitter out.  Maybe it's a situation where at that stage in-game, there is no need to go to the pen and face the other teams' best hitter, so Sim just keeps the pitcher in and not go to the 'pen.  Could it be that Sim will bring in the LH/RH Specialist only when their best LH/RH hitter is up? If batter X is an 85 v Lefties and batter Y is a 83, is it safe to say that the Specialist may only get called to pitch to X and never Y because Y isn't the "Best"?  Just a thought...