Just a thought Chip, but replacing the powerhead on an outboard with a golf cart motor would give you reverse without using a reversing solenoid pack. Using a longshaft o/b would work better off a pontoon deck anyway I think.
Oyster posted
this link in another thread recently, but here it is again.
From what I've read, the outboard conversion's toughest part to DIY is machining a coupler to join the two shafts.
I think you could improve on the o/b conversion by ducting a slower, bigger prop as well rather than relying on the stock o/b cav plate, but we'll see in the spring after I scare up a motor and controller.
I haven't seen the E-drive plans other than what's posted on the website, but I think I'd want to have the mount welded up from steel or aluminum rather than ply once you consider how tight those belts would need to be to keep them from slipping under the torque of an electric motor spinning a prop from a dead stop, but that's JMHO.
All I've done so far on my own project is to get the donor o/b, but another option I've been thinking about instead is using these in a tunnel. On a pontoon, you could use a single motor on each hull with its own battery bank though it would be pretty exposed when beaching the boat. Though I suppose you could rig up a sort of hinged 'trim tab' mount that would be driven down into position by thrust but kick up if a skeg hits bottom...

I emailed Minn Kota a while ago about using these as for continuous-duty applications but their warranty wouldn't cover them in that case. I thought that was odd considering that they get used for trolling for hours at a time...