I'm beginning to think that ELU & SPD are overvalued for DLs by most people. I've never found my D-line to be more successfull with fast, elusive linemen in the DE spot or the DL spot. I've converted LBs to DL before who ended up with 90 SPD (at the D-I level). I've also signed VERY elusive DL's just to test if it made a difference. Their STR & TKL were typically 5-10 points lower than average. The the 50+ advantage in SPD didn't make up for the low STR & TKL, and neither did a 20+ advantage in ELU. Essentially, all these players sucked. If the GUESS formula places any weight at all in SPD or ELU, your guy's rating will be in the toilet since they are both so freakishly low. But if those attributes truly are rather irrelevant like I think they may be, your guy may turn out OK.
When I was in D-III, I always tried to find guys whose STR+TKL totaled at least 90. High secondary attributes could make up for guys whose total was in the high 80's, but I didn't want to field a whole team with recruits like that. With that said, I don't see your guy ever being great with STR less than 40 to start out with, but he could be OK after a few seasons.