I'll attest to that:p. I reckon 100 miles (yes miles) is about max until you need to get out and stretch. 250 to 300 miles a day is ample, which is about what we averaged on the way to Cooma.
Incidentally, I made new bases for Leon from some 63mm x12mm (2 1/2" x 1/2") western red cedar I have at home. Piece of cake, as they are very simple constuction. Plywood under the hessian as Diana said would probably work, but would make the base firmer at the same time, so maybe not that desirable.

