I have this same problem. I have a great saddle...it works wonders when I wear my thin chamois shorts for shorter rides (less than 50 miles). BUT, my PI Ultrasensors which I wear for longer rides, drive me batty. The damn chamois moves around too much...bunches, shifts...very annoying! I'm thinking of trying the shorts in a smaller size, because when it is in the right place, it feels fine. My problem is that my legs are big, so to fit my body, the leg bands are going to be doing some serious 'sausaging'.

I got the saddle right on the first try by doing some measuring and some reading...but getting the right pair of shorts for long rides is turning into a very expensive endeavor for me!!