To the original OP: You will not need a spacer unless you wear shoes the size of canal boats as many brands come in two sizes Sm/Med and Lg/Xlg. The min-toe-clips sold by Nashbar (which I also used in the past) and by Niagara Cycle are made out of very tough plastic, probably ABS like you find on car bodies these days. They have some give but I certainly wouldn't call them "flexy" enough to result in a loss of power. I've used metal ones in the past too. They are strong but somewhat brittle and it is my perception that they don't last as long as the tough plastic ones. Eventually the metal cracks at the front of the toe clip.