And where might these shipper boards be?
I work for a loader board that completely cuts out all brokers. What happens is that shippers save a little and carriers make a nice percent more per load. If you are worried about pay issues use quick pay or a factoring company. You give up 3-5 percent there but the percent you make up for cutting the broker far out shines that.
My suggestion is to dedicate yourself to raising the percentage of shipper direct loads and lower broker loads. Either market shippers directly or go to boards that are broker free.