I was having the same problem and did the same as you. Switched to the look pedals from some old stb's I transfered from a MTB. Thinking a bigger platform might help. What I actully found to help after experimenting with a number of solutions is starp adjusment on my shoes. I have a pair of Sidi's with three straps/buckles. The top one (closest to ankle) I can have tight to keep the shoe on but not cut off circulation. The middle one is loose and the bottom one is even looser. It's worked pretty good so far. Hope it helps.