Okay, a few of you may have read my previous posts on deciding on an engine for my CMPro Extra 300s 90.. and i have come up with the following engine's to chose from, can people please comment on the different engines from either experience or know someone thats used one, and tell me which is the best choice. I am not looking at a 91 as i want to swing a 15*6/8 to 16*6/8 prop.

These are the engines i am looking at to power it: Thunder Tiger Pro 120 and the O.S. 1.08FSR. In order to compare them properly i will put specs of the OS91fx in there too, so you can see why i am struggling to decide.

Thunder Tiger Pro 120
3.5hp @ 15000
35.5oz

O.S. 1.08 FSR
3hp @ 16000
28oz

O.S.91FX
2.8hp @ 15000
19.3oz

The model is spec'd at 3.8 - 3.9kg's or 8.3 - 8.6lbs, and has a wing loading of 76-78g/dm2, and a wing area of 50/dm2. The thing i am worried about is to keep weight at a minimum with the best aerobatic power.. i guess the OS is okay, but the TT is quite a bit heavier than the OS but has a lot more power.. so is the extra 0.5hp worth the extra 9oz of weight in the Thunder Tiger? And furthermore is the OS 1.08 worth the 0.2hp in the gain of 8.7oz? It seems that the power increase doesn't do the weight any justice.. If you take the OS 1.60 for instance it only weighs in at 32.6oz and puts out 3.7hp, which is lighter than the 120 TT but is only 0.2hp up from the TT120 and its a 160?

But there is a big variance in weight between the models.. and given that they suggest an engine from .90 2c up to a 120 4c, then they are basically suggesting an engine weight of between 19-30 oz roughly that is if you take into account the weight of different brands of engines, but in stepping slightly over this mark, regardless of the extra power is it going to make it a pig to fly?? I don't want no million mile an hour landings cos our field isn't really that forgiving for high speed landings. However i understand that usually Extra's and Cap's usually require a little extra weight to balance, is it usually in the tail or nose that they need the weight?

Please help! James.