Good plan and as you say, easy to remove. I used butyl sealant for the floor so that it seals but can be removed at a later date. Butyl doesn't bond like PU does.
I used AL Services floor cross members to add a bit of strength.
Keep an eye on how close the floor gets to the fuel tank sender pipes. Just enough clearance on mine....
Wrote most of this up in one of the links above. Hope it may be of use to you.......