Totally agree Todd, as a long time reader of Radio Race Cars (UK Based) magazine, they race a ton on non dirt tracks. The most common surface for the Brit's appear to be natural grass surface. They also as Todd says use artificial turf and bricks as well. My .01 opinion is that we should look at all possibilities, collect as much freebies as possible and make two really cool tracks that fit our needs and those of others too.
Steve