I do not have it to hand but the D&C "Monograph" series book on GWR coaches shows a diagram of a South Wales 7 carriage set which shows coupling types and bow or flat ends on the carriages. The set is Van Third, Third, Third, Comp, Restaurant, Comp, Van Third. So including the Restaurant carriage from the old range you can get a close approximation to a prototype set. Happily Loco + 7 is the ruling length on my layout!
Best regards
Julian