The average wheelbase ...

... of a Long Wheel Base recumbent is ... 65" to 70". From "The Recumbent Bicycle", by Gunnar Fehlau

The ideal riding position for a recumbent is to have the seat / back of the rider at 120 degrees to their legs as in this diagram, also from Fehlau's book ... apparently the angle of the legs to the road isn't of major issue other than that it's awkward to see, and easy to slip off the seat as it is tilted further backwards ... probably not a good idea.



I think this 120 degree position will be awkward for riding while not pedalling, so the rider will be able to tilt the seat more upright if required ... this all starts me thinking about the frame design - but I must finish spec'ing the drive train & generators 1st ...