Re: Hey, new guy here. Planning builds for 8 bikes on MTB frames. Recommend some pa
Davezilla covered it well.
About all I would add is you might want to rethink using aluminum frame bikes since they are harder to get the engine solidly mounted and securing the chain tensioner properly is also much harder. With a steel frame, you can easily tack the tensioner for total reliability.
I prefer the ride as well, but most people will never notice any difference. Engine vibration can cause serious failures with no warning on Aluminum frames too.
I'd look for a steel frame mountain bike with a normal diamond frame layout and level top tube for ease of building, proper engine mount fit, and best level of hardware for the money. Look for at least good Vbrakes and components.
Be aware most 29'ers will be a pain to mount a stock ragjoint rear sprocket, and might require a sprocket adapter. The kit sprocket is designed for 36 spoke wheels, and most 29's are different.
If more is better, then too much is just enough.
If you can't afford it, build it yourself.