This treads a fine line betwixt scratch and kit, I think. Arrr! Blimey! It's more or less a copy o' a design by Gerald Wallace (Bohica) discussed here and here. Avast! Specifically his 13mm version, me bucko, but mine has an 18mm motor mount; also I used one each 5055, 5060, 5070, and 5080 rings, which is what it says on his diagram, but in fact he used (for one version, at least) 5060, 5070, and 2 x 5080. Blimey! It's nay clear t' me what Wallace used for launch lugs. I chose t' put one 1/8" lug on a standoff near t' center o' gravity, high enough that t' rod will clear t' 5060 rin' and go through 1/8" holes punched in t' 5070 and 5080 rings. Avast, me proud beauty! (Without a standoff, t' two smaller rings would have needed gaps cut out o' them, me hearties, and I didn't like that idea.) Finish is Duplicolor Metal Specks red, rings are Rustoleum 2X gloss black, arrr, and thar be a Testors trim tape line around t' front end o' t' body tube.