Structure - good question--but first - I don't use either of those engines -
I do use singles -a lot --and except for a bit off idle firing pulse induced shake - they are very smooth.
My structures use L shaped spruce longerons top and bottom of fuselage - also the entire fuselage center is a sheet(s) of balsa which runs cross grain to the fuselage.
So imagine an I beam -on it's side.
The engine bearers are angled from the four engine mounting ears to each longeron - forming a pyramid.
these pieces are also L in cross section and are mechanically locked to each longeron.
Th entire assembly is now a large rigid structure . No see saw action in these setups
big slabs of wood are worthless in terms of rigidity .
This is simply an old carry over from control line building .
Mass balance technique -
I never use that setup and my Bucker -- almost 15 years old -never a structural or joint failure .
The composite structures however have a finite life - just like a DeHavilland (?) Comet .
The extrmely brittle nature of the CF sets up fatigue in critical areas - some worse than others
For an electric powered model these are a great match!
my 40 cc tuned pipe Petrel -- 11 lbs flying weight . 1280 squares
Almost all gas wood kit structure follows same old setup - a square motor box to a wing tube - also a non triangulated fuselage structure , which in the forward section relies on the square motor box locked to the tube and sheet sides to carry the load -
easy to do but not the swiftest setup
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