[Jared Russell]

Originally Posted by Joe Ross

The first Q/A answer is in, and it's a good one. We do not have to use a rover wheel for an idler wheel. http://forums.usfirst.org/showthread.php?t=10917

This was an answer I did not expect. Well then - this becomes the most attractive of the various slip detection strategies in my mind (since you can get away with negligible downforce). Keep in mind that the poster of this question talked about a freely rotating caster - non-rotating casters would indeed provide turning resistance (even if slight) and might not be covered.