Hi there! Apologies in advance for not answering your question, as I am wondering the same thing. Have you tried installing the upgrade kit yet or are you doing research still at this point?

I am also working on installing on a 5+ (step thru) and I am noticing that a lot of the connectors are not compatible with the bike's stock connectors.

Did you end up installing the upgrade controller? I'm working on installing one of these on my 5+ step thru and I am finding that a lot of the cable connectors do not match up.