I believe ID on SGs is definitely important, particularly when you play M2M versus teams using an inside tactic. In things like LI and LP, the SG will attempt a decent amount of inside shots. Now, I'm not sure you want to actually try and train your guard trainees in ID at the center position, so like LA-Terfu said, you might have to be content with what training pressure gets you. Well that, and hopefully starting with trainees that don't have 1 ID at teh start.