Val,

I was thinking of doing the same thing with fillets,i still might add a 1/4" sq section running along side of each airframe side,so that each sheet has something to rest on.

I guess the reason for this design,is to allow a free passage of cooling air,to pass engine,and then exit down through bottom cutout vents. i think cooling will be very tight,looking at that grill front!! ,and any added wood to the rear,might prevent a free smooth passage

Anyway i will see how it goes,and like you said,you found the finished structure stronger than first thought!!,i will battle on!

Thanks for input,any other advise very welcome

Eindecker