Hi Russ,
Firstly welcome to the forum, you,ll find its a happy / very helpful bunch of like minded nutters (
builders) on here.
The Haynes chassis is 4inches longer & 2 inches wider than the Caterham chassis so you,d have no problem with your height / size ,
Spud69 is indeed 6ft 7in tall & has a standard Haynes chassis, thats the benefit of the Haynes, much more accomadating to the taller driver , tho i,m a shorty at 5ft 8in
aka as Shorty at Saturn sports cars.
All the best with your build.
cheers
andy