too wide at mid-saddle definitely gives me chafing in exactly the area described in the OP. I don't know what to make of your 'too narrow at the rear of the saddle' thing, however. I've never experienced that. too narrow for .. what?

I would try a different saddle. get one from a LBS with a 30+ day exchange/return policy. move through the popular options. actually, maybe you should try specialized since they sell 3 widths per saddle style. some brands do not do that at all, they have one width per model and shape/features can vary tremendously by model.