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.
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Hot: 2001 Estoril M Roadster
ZCP 19's michelin supersports, ZHP knob, JL 8W3
Cold: 2002 TiAg M3 6mt ZCP 19's michelin supersports, deoranged, dechromed, led tails, ZHP knob, UUC SS v3, GROM, OEM 18's w310's,
fun: 2006 YZF-R6, black