Just passing along my experience and a few tips for converting a Mongoose Argus Sport 26 with a BBSHD kit.

For starters, removing the crankset was a straightforward and easy process that only required a metric hex key (don't remember what size) to remove the crank arms and a 44mm 16 notch bottom bracket wrench. The 120mm BBSHD fits perfectly with just a 20mm spacer on the chainring side, and my chainline is decent with the addition of a 42-tooth Lekkie. I could have shifted the chainring in another 2.5mm if I had used washers or shortened the included spacers on the left side motor bracket, but I really can't complain about the chainline as it is. I went with a big 52v 28Ah triangle battery for the maximum distance between charges, and I quickly decided that the included Velcro straps were not appropriate for such a heavy battery. I ended up mounting two 1/8"X3"X12" aluminum plates on the bike's bottle cage mounts, and I used titanium screws so they wouldn't break under the weight of a fifteen pound battery. Then I just strapped the battery to the aluminum plates with zip-ties, and it feels every bit as secure as a HaiLong battery mount. Plus the aluminum plate on the seat tube provides a nice place to safely zip-tie the wiring. I originally planned to bundle the wiring in the gap underneath the battery, but I think down the side of the seat tube is better.

I had a heck of a time getting the brake sensors to work on the Tektro Auriga brake levers, and finally had success after seeing another example of the magnets mounted standing up instead of lying flush. They look odd mounted like that, but they work flawlessly. And as you can see, I couldn't stick the sensors down and had to just zip-tie the cable as close to the sensor as possible. Not exactly an ideal installation, but it's the only configuration that worked for me.

And finally, I put the shift sensor up near the shift lever. This required either a y-splitter to tie into a brake sensor cable, or an extension cable to reach down to the proper shift sensor plug. I opted to get an extension cable, and the installation was fairly easy. Do get some cable crimps so your derailleur cable won't unravel, and do get a proper cable cutter since it's difficult to get a clean cut without one. I learned that lesson the hard way.

This bike is a beast, and that's what I call it. I'm very happy with the way it turned out, especially considering that it's my first build. If I had it to do over again, I would have opted for the 40-tooth Lekkie and drive cover combination since I could have got the chainline even better with it. Thanks to Johnny for the advice and prompt shipping, and I hope this info is helpful to other DIY eBike builders.