I thought about drainage holes.  Do people put them behind the seats in the foot well or in front?  I would have thought that you weld in some sort of insert, I thought a bath plug hole plus plug might be clever, what do others use?

Under the seats I have two plastic sink drains for caravans, in the footwells two sink plugs

Tips if using sink/bath plugs
Dont use the captive plugs like mine, slightest bit of dust they jam
You will need to make and weld in pieces of tin as they need a chamfered hole (or get in there with a big hammer)
Make sure you get ones threaded right the way up as they often have a long unthreaded area to fit in a ceramic sink

2 M8 holes well painted on the edges in the rear foot wells will do, you could go M10 and drop a split pin in to keep them clear.

My Buggy comes out of hibernation in September and goes back in in May.
Reason - Trials!
Motorsport for buggies (and others) in the winter months.
http://www.youtube.com/watch?v=ksZsuwFVroE

My Buggy comes out of hibernation in September and goes back in in May.
Reason - Trials!
Motorsport for buggies (and others) in the winter months.
http://www.youtube.com/watch?v=ksZsuwFVroE

That looks like fun ! 

That camera mans a right trooper. Took a direct hit from a rock!