Making a SUP conversion kit from a trolling motor

Hey.
I’m working on making a electric drive conversion kit for my SUP. I did find the many $500 kits that go maybe 3mph, but I can paddle that fast, and want to be able to both go faster and longer.

So far I’ve bought a 55lbs thrust trolling motor (50amp max, up to 9mph), a 50h LiFePO4 battery. I’m adding a volt/amp meter to the waterproof case, a jetski type emergency disconnect lanyard, a 4 channel remote which I’ll waterproof (spare remotes are $5 each). I’m going to use solenoids to physically turn the original motor speed control inside the battery box, and use one channel for a power cutoff vs. needing to multi-press to get to no power. I’ll probably disable reverse speeds.
I’m working on designing different ways to attach to the board. I don’t think a fin box only connection would work for for the amount of thrust, and the motor is like 15lbs. I want it to be able to work on most boards, and ideally be able to remove while in deep water in case there is a failure and I need to paddle back.
So far, this is a pretty affordable project - $180 USD trolling motor new, $400 50ah LiFePO4 battery, $100 other parts, $50 watertight box.
I do hope to be able to work on tweaks to get more speed, but my goal is really to be able to go long distances (exploring), with the ability to play with the dolphins (they seem unable to go only 3mph).
Clearly 9mph is not the 20+++ I’m seeing people getting on this site, but there doesn’t seem to be any options at all for the mid-range 5-15mph.
Anyway, I’ll be posting pics on my instagram site HawaiiWes68, and I expect to have this complete and operational in the next 2-4 weeks (before Oct 21, 2020). I’ll be headed to Mexico for the winter (staying in my RV on the beach there for 6 months), and so it must be done for that trip.
I don’t see any other postings of this type conversion, has anyone done anything similar?