My reason for using an old twin shock XR is that they are short, light, have a short seat height, have a lot of clearance and sufficient power. Slipping through close trees will be easier for an old guy and the bike will be easy to pick up when I fall. The only negative is that I have to make parts because they are no longer available: side panels, a rear fender, a decent looking seat and a chain guard.
Fender, side covers, and chain guard