I`m not much of a builder, but I have designed guitars for other people and for some manufacturers and I know that one of the most important things about guitar is how comfortable to play-wear it is. Make a template for Your bass original size. Best some thick plywood, just contours, put some strap on it and hang it on Yourself. I think Your bass is wrong balanced and it`s gonna pull over head (Head region will fall down as You do not have much weight at the bottom, I mean bass bottom I do not know about Your bottom), also, How shall you hold it when You sit, I have understood that this one sided wings are on the upper side, I like crazy shaped basses, but Yours seems probematic.
As I have started building guitars myself recently beside designing them, do not EVER cut anything before You get all parts and lay them down, and measure and draw everything and rethink everything few times and just look at that for few days, i have ended with exotic wood night table instead with my first guitar because of that. As I have been making bolt on with neck I have bought, it survived, if You make construction mistake on neck through You`ll have a lot of expensive scrap wood.
Do not spend fortune on brand name hardware there is a lot of good parts of anonimous manufacturers that make quality parts especialy at USA.
Best regards