Exile,
Welcome to the boards, although I dive a well constructed, professionally engineered and manufactured Rebreather, so therefore cannot even fathom the process you are about to undertake to DYI. I do know there are quite a lot of divers on these forums who have designed and built there own units, so I'm sure they will be able to help you with the dos and don'ts of self-construction. I've got to say, my hats off to them all, there is now way I would have the talent or brains to make something I would bet my life on at 1 meter, let alone 40+.
Good luck, with the build, and of course, safe diving. And if you ever make it down to Melbourne to enjoy some of our fine, warm tropical waters with perfect visibility and world-renowned wrecks, look me up, it's always more fun diving with an unconstrained Rebreather diver than sitting around waiting for OC's to clear their deco
.
Cheers,
Michael