interesting thread, thanks for the link dave
i am planning to build a TD to tow behind my VW splitscreen campervan, its slow enough at the best of times, thus my aim is to keep it LIGHT
so the A-fram design looked ideal, i have now decided on a Square frame, its only 1 short length ( 1.2 M ) extra in metal work, i it will give the frame that squareness

if you get what i mean
its then going to be the TD shape without the gallery ( but with cupboard space inside ) as we cook in the campervan, its only going to be a extra sleeping place for 1 adult and 1 child
lightness is the big key for me, so the lightweight frame, 12 mm floor , 12 ( or 9 ) mm sides with the roof out of the really thin stuff ( is it 3.4 mm ) , i fancy a ali roof aswell ( i know this is going against the lightweight idea, but i fancy the look on it )
500kg suspension with 10" wheels, i would have liked to have fitted 14" VW wheels, but i dont know how easy that would be
i am putting together a metal cutting list right now, will get it ordered ( i think i might try 1 of the ebay metal sellers, unless any1 knows of any cheap online UK sellers )