The plot thickens. According to Red* (@Redax)this
foot peg/ gear change setup is aftermarket or non- standard, I think he put it. See pic. The "scottish"? origin midmount plate & sidestand he has in stock would need serious mods to work. Centre stand a problem too I believe. Would appear rear sets is the only way to overcome the problem, sadly my broken bones will not handle the riding position over distance any more.
It's worth trying a forward mount unit methinks despite the shoddy design ... anything out there? Note that a set of Koni shocks, Type 7610 are in place (look new) so I imagine the longer 21.5cm length would be in the ball park.
* Red had the 3C in the workshop for a couple of days. Talk about a legend ... I picked the bike up running rough, would not idle .. sounded like my 20HP V twin Intek, Greenfield Ride-On

test ride was a total riot. Red handed it back all sorted, a little lumpy & now needs running in given the timing was out 18 degrees! Go figure.