Has anyone purchased a custom shelf from Middle Atlantic for their rack? They only list the Model 770 in the custom shelf area, is it the same dimension as the 7700?

The 770 and 7700 have the same dimensions (both are listed as being 17.2"x7.75"x18"), but they have different faceplates (obviously). I searched here at Middle Atlantic, however, and found that the 7700 was listed (the model number for its shelf is RSH4A5X OUTLAW MODEL7700, and it takes 5 rack spaces). The list here has a "770" right after the "7500" but it's either a typo (much like the Outlaw "220" a short ways above it) or it is a shelf that works for both amps.

Thanks for the insight, that's what I was trying to confirm. Is the 7500 also the same dimension as the 7700 only lighter?

Yep - the two share the same chassis and a lot of components (same amp channel and I think same transformers), but the 7500 just has two less channels inside and a little wider spacing of the channels that are there.