13 lbs is where the 40 stil has unlimited performance --I have two 40 ZDZ models with internal mufflers one 13 lbs one 13.25
One is a 260 Extra the other a Cap232
Other than appearance - the current pattern stuff is really not any different than the semi scale IMAC models --performance wise . This is not a slam at any design - just do a close look at both -you will see what I mean
The fuselage area distribution is OK on any of the current stuff - just make a shape that is pleasing to you and stick the flying surfaces in about the same places-
basically copy the general layout of the current stuff
canopys /wing tips etc., don't amount to hill of beans
just make it look good . wide narrow whatever - wider is easier to make stiff tho