Track Spec's (indoor dirt track, 1/10th-1/16th)

[Karting]

Hey, im sure you get quite alot of these, quite often but im going to ask anyways.

I may be able to get use of a warehouse approx 150sqm in size (family own it but it empty atm).

Im looking at building a indoor dirt track for my 1/16th Off Road buggy's and possibly 1/10th (depending on size needed). My first plan is to build it for use for myself and friends but i could open it up in the distant future, depending on intrest.

(Bit about myself) I work in the building trade, so getting materials and actually building the track wont be a problem and i do have friends who run building merchants so materials can be cheap.

The questions i have are:

What is a good size track for 1/10th-1/16th (width/length) and could i get it in a 150sqm area.
What is the best type of dirt/clay combo to use.
Would there be intrest around the Heathrow area for a indoor track around summer/late summer time?

Once again this is all provisional that i actually get use of the unit.

Thanks