Curious to hear if anybody chimes in. They look like a blast and seem to be relatively safe. I can't imagine it would be as expensive as what you list for annual costs for your RS.
08 E90 | Jet Black / Black | 6MT
Mods: RAC RG63 w/ Pirelli Corsa 255F/285R | Akrapovic Evo Exhaust | OEM Blacklines
Winter Setup: OEM 18s w/ Nokian Hakkapeliita R 245/40-18