The fillets are quite narrow, only a foot or two, the Firecracker's are rather wider like a Cherokee. It's got elements of lots of the suggestions but nothing gels! I know Paul Nalson supplies aircraft for films and I did wonder if it is a "bitsa" put together for something but it does look to sophisticated. The Ryson Cloudster crossed my mind but nope, nothing like really, plus only one was built.
Perhaps I should email him and see if he would be kind enough to supply the solution!