Will have to install a boot cover, for IVA requirements, (as was for SVA, I believe).

What material is recommended? Alu sheet, heavy gauge C/F sheet, or good ole MDF, covered in vinyl???

Will also have to fit fuel filler + cap into this cover.

^^^ all of those a good. depends on what parameters you a building to? want it to look nice? wnat it to be light? etc.

I would suggest 2 mm aluminium covered with pvc cloth.

not a fan of MDF which is solely for making crummy furniture and/or dog kennels

I agree MDF is way heavy and you really don't need the back of a 7 to be any heavier... (unless you've got a boat anchor at the front in which case it's a sensible precaution to stick an MDF anchor on the back!!)...

If you're using MK bodywork I'd go for a tonneau cover which nicely covers the rear > side panel join

Fake carbon fibre sheet? Its light, cheap and looks ok.

Thank you, all, for these replies. Will check out the fake C/F sheet idea.