Sounds like a plan.Thread resurrection - sorry...
I'm just preparing to carry out floor insulation and lining in my van so this is all good info. I'll do as @Superowls and packer with 9mm and silent coat all the gaps.
Just looking at those packer kits and the price is way up - now £45 +VAT for a kit, and they're on back order. It would be interesting to know the total area of ply needed - since an 8x4 sheet is £24 from B&Q (and that's going to be way more than needed).
My plan is - 9mm ply packers - 2mm silent coat on the remaining exposed metal - 9mm ply floor (since I've already got) - and Altro floor on the top.
Hopefully a Kombi step covers that?
My Kombi step & rear threshold fitted straight over no probs
If you're happy cutting up the ply then you might as well do it yourself and save a few quid
I did mine in October so didn't fancy a day on the drive measuring, cutting & sweeping up so was happy to pay the extra for the convenience
Just weight them down overnight after you've stuck them to make sure you've got a solid base to screw the ply floor to