I guess my question is, if you don't have the Jumbo Joe yet, why not just get a WSM?
A Jumbo conversion is going to be the same size as an 18.5" WSM, right? And the WSM is designed to be a smoker. The Jumbo is designed to be a grill.
The mini-WSM built on the SJS or SJG platform fills a niche for a smoker smaller than the WSM.
I can see the lure of doing a build, and if it's what you really want to do, Chris's advise is spot on.
My Boys: Joseph (EI); Andrew (EE); Daniel (EE)
My Toys: 10 WSMs (B, C, DH, DA, EZ, DZ, EO, DU, DR, EE/DU mutt); Brinkman Cimmaron; Chuckwagon Cooker; 4 22.5" Bar-B-Q-Kettles; 1 18.5" Bar-B-Q-Kettle; 1 Red OTS (H); 3 WGAs (EZ, DE, N); 3 SJPs (DT, DR, DR); 2 Smokey Joes (A, K); Genesis Silver C (DU).
"For when democracy becomes tyranny, those of us with rifles still get to vote"