Nothing at all. That's why you see them jumping around on the various vacancy bids, too. Many are 'staffed' on equipment they're not qualified on. Perhaps I'm misunderstanding you though.

As long as they're in TK, where they show up on paper has no affect on their compensation. What matters is what they could hold, or more accurately - where someone junior to them shows up. Nearly all the SUP you see staffed as 76T, 320, etc... are most likely receiving 787/747/777 hourly rate ($168-ish/hr) which is the current 9 year widebody FO cap.

Currently, every single 76T instructor has someone junior to them on the widebody pay scale (777/747/787).

The most junior 777 instructor, can NOT hold 777,787,747, but CAN hold 757/767 so that's the blended rate he receives. Clear as mud? :-)

Sorry for the thread drift...