So here's a little update. I've known from early in the design process that the SEGA JVS I/O pcbs have the 12v and 5v power rails connected to the 60 pin CN3 connector as well as the dedicated power input/output connectors. Because of this I connected the 12v and 5v rails to the 60 pin connector on my adapter boards also. I did some current draw testing on the SEGA I/Os that I have here, and did some math on the amount of power that the 60 pin ribbon cable can carry and determined that the separate power cables are not actually required. This means that going forward I will not be providing the power cables which reduces the time and cost to manufacture these adapters. I have adjusted down the price of the kit in accordance to this change.
I've also listed these for sale on my site now instead of doing these through PMs, this makes ordering and shipping much more streamlined for me. A small batch is available now on my website and I plan to keep them in stock regularly.