Thanks for all the help and suggestions. I do like the idea of fitting seats from a production car - the MX5 for example. I dont have my chassis yet (well, I do but not at home - long story!). Could someone tell me how much room there is to play with in the sportster in terms of available width?
I was looking at this for example:
http://www.ebay.co.uk/itm/Mazda-MX5-...item45fbadf955