Fact is, despite the current build using metre lengths of tubing, the overall width that includes the stubs on which the motors will be mounted runs to 51" anyway, precisely the same as the outline in the previous post that has rather more to commend it.
On the other hand this one has a track just 41" wide and therefore fits snugly on the trailer, so it seems a shame to scrap it especially in view of the fact little of it could be repurposed to suit the bigger build.
It's also something of a fag having to build any number of prototypes, especially as its a scale demonstrator, or at least here in the UK. However as I've two complete sets of motors, the obvious solution would be to build two working prototypes, which if nothing else reinforces the versatility of the build methodology.
Onward and variously upward...