Thankyou for all the feedback. I might have to reconsider!
Lots of good reading and links, thankyou.My untrained brain was concerned with the overhang - but very valid points - don't want to make it too ridged or take too much weight off the driving wheels.
In the spirit or trial and error, while not introducing too many variables, I should concentrate on getting the primary springs correct and functioning and then think about the issue of secondary springs and body weight.
I will have a think.
J