box squats to get the right form isnt such a bad idea. i know rippetoe doesnt advise this but i do believe that there are more ways to skin a cat.
i started my gf doing ass to grass box squats and she's progressing pretty well. in about the next 4 weeks she will be able to do 8 sets of 3 with 95....pretty good for her since she weighs only 120. anyways, my point was that Eric's point sounds good.