RE: 1/5 scale SIG CUB engine choice
I have the Sig 1/5 scale waiting to be built and I am planning to power it with a 52 4 stroke engine or possibly the new O.S. 56 4 stroke. IMO that's the right power for scale flying. If yours is a clipped wing and aerobatics is your cup of tea, than a larger engine might be appropriate.
DaveB