My tip is to have a good understanding of the rules and some experience of dealing with VOSA and DVLA as this always helps. I have been "fighting" them for a few years with everything from a i/c powered Sinclar C5, to trikes, hot rods and many other "specials"
My tip is to have a good understanding of the rules and "help" the inspector to apply them. They are never wrong just mistaken.
VOSA and DVLA say a car is made-up of 6 major components each carrying some points which total 14 (just look at the form you have to fill out). To retain the original registration the original "unaltered chassis" and two "original major" components must be retained making a minimum of 8 points.
Chassis (unaltered) = 5 points
Suspension (complete) = 2 points
Axles (the pair) = 2 points
Steering = 2 points
Transmission =2 points
Engine =1 points
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TOTAL 14 points
NOTE= the body work or body panels or body tub is not mentioned or included as part of the original car unless the body is a monocoque body which means it is actually a chassis (5 points).
So the body and it's components are not relevant at a DVLA VIC inspection provided the chassis remain "unaltered"; ie the body and it components it fixed/bolted using the original body mountings points thus the chassis remains "unaltered". This is why the rear chassis rails on the Ribble kits are left in place until after the DVLA VIC inspection.
VOSA and DVLA will be looking for the "original" and "unaltered" components as per the rules, and again the body tub or frame is not included as it's not in the rules.
These kits use every "original" component and these are "unaltered" components so scoring 14 point of the available 14 points and this is why they normally pass the inspection with ease and it's normally only a chopped or welded chassis that can cause some problems.
My steel cage frame will be and has to be bolted to the original "unaltered" chassis using the original mounting holes as per the DVLA rules.
My fiberglass body will then be bolted to extra shaped supporting bracket welded the steel cage frame so the fiberglass body can be un-bolted and removed for any major work.
The steel cage frame will always remain bolted to the chassis as it will still carry the steering, pedel assembly, fuel tank, seat belt, ect ect.
As far as cracking goes a bolt will allow for a little movement but a bonded joint is fixed so will not and the area around the bond will be much stiffer than the surrounding fiberglass, perhaps adding some stress the body work, only time will tell.
I think after the DVLA inspection and on the first body removal I will then weld the steel cage frame to the chassis just for that little extra strength I can't do this before the inspection because as it's welded as opposed to bolted it would be classed as an "altered" chassis
I personally would rather have a joint that I can see and know how it's doing it's job than one I just hope is doing it's job.
I have said, my steel cage frame and my fiberglass body because it is mine and as such I will build it the way I want to just like all kit cars are built. If it fails and I am wrong then I can eat humble pie as well as any man.