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