[HandyAndy]

Baz-r.

basically you are right in your thoughts......... the tubes used for the ally tub are not needed for a GRP tub,

but there is an extra tube (supplied in the flat packs) that is cut to size for fitting a GRP tub.

its a nice position to be in, with the choices you have mentioned...buy steel/flatpack or fully welded chassis, it all depends on how much/how little you wish to do & also your build budget,

if you have any questions, don,t hesitate to get in touch. (regardless whether you go buy steel/ flatpack/built chassis)

good luck in making your choice of which way your build will begin by.

if it helps, i have some photos showing the rear of the chassis for fitting a GRP tub, let me know if you want them put on this thread.
cheers
andy