I would add that being tail heavy is the norm for all of the current ARFs.
The new Sukhoi by H9 is a beauty -but balance is based on using an engine weighing about 5-6 lbs.
To get it to balance with a 4 lb engine - everything goes forward - ditto for the Aerowerks ARF 540.
As far as power and smoothness and going for quiet-by using a quiet can setup -some of these offerings will cost you $1500 before you get it.
all together.
The cowling on the 540 ARF does not allow for engine fins on top - using a DA100- so you should consider that--I presume you have the ARF ?
You will probably need some surgery -no matter what engine you pick.
For Colorado Springs - I would opt for all the power you can squeeze into the cowl-
Good luck -and don't buy any pigs- in- a -poke .