Guess you are referring to the 55" blue-yellow 50 size model. I have one but it is still in box. My starting point would be a 55ax with 13x4 prop and standard size servos on all control surfaces with reinforcement for the firewall and the LG Block. I would then explore a larger engine say a 72A or thereoff if the 55 didnt have sufficient power for this very light airplane which is very unlikely

Ameyam