I'm about to order one for my 4777 next week. In a couple of weeks I should have some thing to say about it. My biggest question is about how to jet it since I have straight leg boosters now and the Proform main body comes with downleg boosters.
I love that thing, I picked up 2+mph over the 700dp. The downlegs are basically just for improved throttle response. I think it comes with 72/84 spread, same as a 750HP series. I spoke with Braswell about them and they use them as well. One tip when installing it, pull the alignment pins from the baseplate. The holes are not deep enough on the body, braswell said to just yank them and get a perfect body to baseplate alignment. Adjustable air bleeds are very nice to tune with.