RE: DA-85/ Extra
The popular trend is to use the 85 for 33%. Use DA 100 for 35%. The two are very close in power to weight ratio, so there are many variables in the aircraft build/setup that will determine the best use of each engine. If you set up the 35% to be very light and ran a tuned pipe it would be fine. The difference between the two scales will be about 3-4 lbs.
Adam