I have a trike and enjoy the ease of riding it. But I miss the 2 wheel ride so I bought the Legup system for my Harley Softail Delux. This allows me to enjoy the bike ride and not have to worry about holding 700+ lbs up when I stop. Also I can stop and go in traffic with both legs up. You see I'm 70+ with a bad shoulder and knees that buckle. I have been told by many that the reason they have quit riding is the same reason why I installed the LegUp System on my Harley.

 

Trike it and enjoy the ride.

 

Three wheels would be his best and safest bet. Many of us have trikes for leg, knee,and back issues, so someone missing a foot would be a good candidate.

If he tries two wheels or the retractable wheel gizmo, and falls off he will never try again, and be more depressed then he is now.

He is better off trading for a trike or getting his converted if possible.