I took the OEM 75% beater drive and switched the pulleys and made 125% out of it and they work well. Makes the machines more noisy however. What is the price of the PF parts kit? Deere was I think around 250.00
IMO 150% is a bit much to speed up the beater. There's a good chance you could run into some vibration problems with that much speed. Maybe you would have some trouble damaging your edible peas? I also prefer reversing the OEM slow-down kit. Either way, to cut down on vibration take a slat out of your beater and vaccum out any dust that has accumulated.
When I talked to PFP about the beater kit he said some frame modification was needed to make to front pulley fit due to its large size.
I put Deere's kit on backwards on my 9650 and I like it. I havn't cut wheat, only milo. It seems like I could push it harder without plugging the cylinder. Acording to the yield monitor, I cut at the rate of 2,500 bu/hr (peaks of 3,000) in very good milo that had been completely killed by frost. That was about 6 mph with a 25' header.
And yes, beacuse of pulley sizes there is almost no room to install Deere's kit. It fits like it was sized to be exactly the maximium size that can still be installed. I don't think I would tackle the mods necessary to fit one with more ratio.
I don't know what you would gain from even more beater speed. The cylinder capacity is the bottleneck with Deere's kit installed.