If you are still considering battery mounting options, I used these clamps on the Schwinn Meridian trike that I converted to electric. A couple of bucks each at Home Depot/Lowes. I used some padding around the tube to avoid paint damage.No doubt. No doubt. I do tend to delay gratification while I analyze a toy purchase/project to death, but I also find that that's all part of the fun of toys. Should I die before I obtain an e-bike my afterlife garage is already adequately stocked.
Having another look at the bike, anyone think a decent 48v battery might fit behind the seat post? Hadn't considered that placement. I measured the seat tube from the lower top tube to the bottom bracket, and it's a meagre 12". Looks like I'd gain an inch or two flipping the battery around back.