If not genuine Di Marzio Super Distortions they sure look like a damn good copy. Thin sound may be due to shape of guitar and lack of timber in all the right places.

I had an Ibanez Flying V with a Di Marzio SD in the bridge position and whilst you could dial in some good sounds the whole thing sounded a bit thin and shrill. Dropped the PUP into a Strat Richie Sambora style and wow, huge sound and made a massive difference. Need to remember that a lot of DM's of that era were mostly mid range boosters and sounded awesome, mostly in LP shapes.

Tend to think body shape may be contributing.