You can screw it into the rear seats. (drill holes first, some parts of the seats have more backing than others. Dont use screws over 3/4 inch). Mine are just bungee'd in for easy removal. Velcro may work but you'd need a lot of it.
Hot: 2001 Estoril M Roadster
ZCP 19's, ZHP knob, JL 8W3
Cold: 2002 TiAg M3 6mt
ZCP 19's supersports, ZHP knob, UUC short shift GROM, OEM 18's w310's,
http://absolutehid.ca hid kit