i think that 2k on the entire underneath is probably not a good idea. it dries really hard, you need something fairly soft and matt finish underneath so that stones and shit bounce off rather than strike it really nicely and chip or shatter the paint surface. maybe some stoneguard or similar product is a colour you like is the way to go. good for sound insulation also. my mate has just done his undercarriage and rather than going crazy on the lot he just painted the driveline. engine block, tranny, tailshaft, diff, fuel tank all in 2k. Ill put some pics up when i get round there next. looks pretty cool