Apricot Slice, that is one neat build! As for the points raised on legality...
This car is eligible for GT12.1. It does not come as a kit so it is not subject to the price limit. It has "additional parts not supplied in the rolling chassis kit" as is allowed. It has no diff but it does have "replacements for other parts." Whether we think it is a VRX with a Supastox front end, or vice-versa, is not relevant to its inclusion.
One can argue that it is not in the spirit of "This class is based on the principals of close, fair and
low cost racing." (as it has cost a lot more than buying just one of those kits) but that is not a rule, just an overall description of what the class is for.
I also agree that the chances of something like that beating the pants off the competition are low. With 930g of weight, a fixed camber at both ends and effectively cart axle suspension at both ends, the handling is almost totally reliant on the tyre contact patch, and that's the same for everyone. As for motive power, so far we find that they are all pretty much on a par once geared for a good lap time, and not just top speed.
However, we will not be seeing that car in any National any time soon, since as far as I can make our neither the motor or the speedo are on any BRCA approved list.
Sorry Slice, couldn't resist!!
Seriously, it is still an impressive build...