I have a hidden hitch brand trailer hitch which was $119 at autozone. You can buy bike racks that slide into the hitch, which you can remove when it is not needed and never scratch the trunk, or even see teh hitch. Another possibility is get the trunk covered with that clear tape they do on new cars as a semi-permanent bra. Check my page for pics of the hitch. I have the hitch bar installed, but you can see where it inserts. Check the exhaust videos which show it best.
http://picasaweb.google.com/72chevman/CarStuff
_________________________
03 GT, STB, GM HD sway bars, 35% tint, GE893(37watt)fogs, Flowtech Terminators, 180 T-stat, ZZP DP & PCM, Ceramic PLOG & Crossover, 18" glasspack, 2007 17" Mustang Bullits 235/55/17 Pirelli PZero Nero, 12" R1 D\S rotors, gutted air box, GTP radiator