I wish I would have mounted a ZDZ 50 on the Patty. It's a lot more powerful than the 40, and I should have not ended adding 12 oz. of weight in the nose to balance. The Lanier Yak will probably fly great with the ZDZ 50 if you shave a pound or so off the total weight. I think the Evolution 58 is about the same weight as the ZDZ 50, with 3.5 more H.P. . 3W 75 cc engines are about 1/2 H.P. less than the Evo, and over a pound heavier. The ZDZ Super 80 is about the same weight as the Evo, have 1 more H.P., but will set you back $825.
Patty can be balanced even with 160 fx on the front. You can use one rudder servo or go for a pull pull or put the battery in the engine box and get rid of the 12 oz. This will change the performance drastically. The evo58 is not the same weight with zdz50 it is about 1 lb heavier. I think it is the better choice for power with 1 lb weight penalty however one should see the flight performances with a both for a sound comparison. BTW do you get 8.5 hp with a tuned pipe? Which prop do you use? My friend have a zdz80 on a comp-arf 2.3 extra and he can not get 8 hp with 26x10 bolly wood and pitts mufflers. If this engine is that powerfull with stock mufflers than it would be a the first choice for all airframes designed for 75-80 cc engines on the market.