uh, which version cassette did you get? I was an original indiegogo backer and the cassette was a shimano 7 speed 14-28t freewheel - this one:
http://www.amazon.com/Shimano-MF-TZ...368&sr=8-14&keywords=shimano+7+speed+cassette
I can't tell from the photos on their current website, the motor is now wired on the gearing side of the rear tire?
Oh wait, now that I think of it I recall running into this issue! I drilled out the center of the freewheel removal tool until the wire would go through if I recall correctly. I had a thread discussing some of the work I did on the bike in this sub-forum (don't have time to search for it, but there isn't much to look through). The cassette will be really solidly on - solution to remove it was to place the tire with the removal tool on top of my vice, lock in the tool to the vice and use the tire as leverage - worked like a charm (this idea was from some of the youtube videos I watched about it at the time).
Anyway, hope that is of some help. I would recommend the DNP 11-34t 7 speed cassette (11t are hard to find, and this one is a solid range for a 7 speed) - you can find them on ebay reasonably priced.