You wont get the needed ground clearance with the 45cc engine. I break 20x8" props on the big lift, so only use 18x10 on the 35cc. The 45cc would use 22" or even 24" props. Way too much for that poor Big Lift.
Power is more than adequate using the 3271 muffler, so I got rid of that ugly tube alongside the fuse bottom. Total weight went down as well with ~200 grams. RPM dropped from 8000 to 7600, which was quite acceptable.