The rough surfaces under most vehicles create lift. You can smooth the surface or block the flow over it for a net reduction in lift. I say block because the ground in concert with the dam does just that, forcing the flow around. Research "ground effect" and "boundary layer". In your case, I'd make the bottom as smooth as possible without places to pack snow.
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Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS
viewtopic.php?f=5&t=13225&p=134742Simple Spring select
viewtopic.php?f=5&t=11815LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12