I'll hopefully be tackling this job next weekend, how much did you guys cut away of the actual floor?

I have a sheet of ally to replace with, is this just bonded in place or should I use rivets or any other kind of fixing?

 

I would just cut out enough to remove the spare wheel well leaving a flat surface. How thick is your ali?

I would use a good adhesive sealant and ali pop rivets too.

Of course once you have a flat boot floor there will be a natural area towards the rear of the car which will act as an air dam unless you do a defuser or cut that away too.

 

Yes sorry, there will be a large diffuser being cut in shortly after.

I think the sheet is 3mm.