Rubber does work as does foam. It grooves up nicely but you do not see the groove as well as you do on carpet. We have run multiple events on it and were very very happy. If you are buying ultimately carpet will be cheaper and some what easier to put down and take up if needed.
Do a you tube search for MMR challenge, 2009,8,7 were all on rcp
Team Tekin, Team Scream, Paint By Mike, Team Mölzer Mowery Racing, EA Motorsports, Speedmerchant, TQ Wire
MMR Direct Minneapolis World Class Indoor Race Facility.
On Road and Off Road racing year round.
Check out You Tube mmrswracing. Every qualifier and every main uploaded at the end of every race day.