Is this for home printing? I think if you remove top solid layers and set infill to 0, then slic3r will treat your model as hollow (not sure if that works with supports and stuff).
http://slic3r.org/blog/tip-printing-vases
SD2 Sanguinololu 1.3a atmega1284p, wood platform, lawsy's carriages, braided fishing line, pallet wood overhead spool mount, carboard/magnet enclosure, glass bed, E3D v6, bed levelling knobs, extended z-stop, 25A DC-DC SSR for bed heater, everything fixed to the SD2 frame, marlin firmware with some adjustments and extra failsafes enabled. I'll never give up on you, little printer that could(n't)!