DS you will need to tell your insurance that you have fixed plant in the van as it changes the risk - ie more likely to be nicked.
Drill a 3mm hole to ensure you will only get the floor and not a structural member, poke a piece of wire through to see where it comes out.
AS I said in the previous post if you get the wrap you can hold the pipe when the engines running. The wrap needs to go through the floor also to protect the floor board - I have a 45 hp blowing through the floor and thats fine.