I got it working!! I took out my soldering iron and very slowly went through and reflowed both SH1 and SH2, and boom! The entire thing started working! I'm so stoked!!
To be fair, I have yet to run into a product from you that entirely didn't work, at least not without well documented warning prior. I've run through a System 16 multiboard, CPS2 multikit, and both AES and MVS carts, and all have eventually worked. Add ST-V multicart to that list.