Maybe this is old news but I just saw it. Corbin has a seat for the C-5
http://www.corbin.com/re/
We supplied the bike for Corbin to develop the C5 seat on. We've sold I think 6 of them. Most are to riders who are inseam challenged and want to be flat footed and, have a nice period looking bench seat.
The bonus is the set of included saddlebag mounting rails I asked them to create that fit the RE bags or most strap on type bags.
They even clear the upturned home market exhaust. Something the stock seat set up won't do.
One can add the passenger backrest as an extra cost option.
We have one "low" type in stock if anyone would like a new Corbin at a bit of a discount.
Most Calif. customers order thru us then take the bike to the factory in Hollister to get the seat made custom to be low or tall, wide, narrow, or whatever suits them and to choose the material they want. No extra charge and start to finish in 5-6 hours or so.
I've sold Corbin's for 15 years, ridden on them since 1985.
3 of my bikes have them right now. Me? I'm happy.