I finished converting my 2008 Specialized Crosstrail yesterday and went for a test ride. It's a BBS02 750W with Eggrider display, 48V 17.5ah Hailong battery and I installed the gear shift sensor.
I had a couple issues and fewer that I expected. I had to take the bike to the shop and have them remove the drive side bottom bracket. They put a 4 foot cheater bar on the wrench and had their heaviest guy jump on it. I'm not feeling too wimpy about getting help with that. Then the motor wouldn't go through, and John shared this video https://youtu.be/FlSuerBVXXs Once I got the 33 mm hole saw, it took a couple of minutes to ream out the bottom bracket and fit the motor. I might not get an A+ in cable management and everything works!
For me, having the bike stand so I could stand while I was doing most the installation made a huge difference. I recently had hip replacement surgery - the bike is part of my recovery program - and my range of motion is still limited. I will be mostly riding on the street, and I've used the programming features of the Eggrider to limit the power output and speed for the limits here.