if big mtn means the same to you as it does for me, someone who is 6'1" and 180 should have a longer ski than 172 (lizzies). I'm about the same size and i'd say you can't really go below 180 really.
here's a list for ya:
(they're all about the same width give or take, stiffest to softest)
187 4frnt msp
183 mvmt gladiator
185 volkl bridge
186 dynastar big trouble
183 atomic pimp
185 rossi brigade/bc
186 fischer misfit
185 nordica enforcer
182 salomon gun
185 armada arv
these are all pretty foolproof options and if you're really concerned about them being too long, mount closer to centre- you can then remount when you realise longer=better! you'll just have to narrow it down based on your prefernce stiff/soft and test em if you can to see which you like best.
i wouldn't go any skinnier than those i listed above, but if you felt like going wider...
(again, stiff to soft)
183 volkl gotama
186 rossi steeze
182 4frnt vct
188 jp/julien
181 scott p4
182 line sfbacon
i know thats a long list, but you need to figure out more clearly what you want out of the ski, then more precise recommendations can be given.
183gotama