I have a 48' Wilson flatbed with two 3,250 center sump tanks.  I use a MixMate tendering system with 6 inputs as well as an inductor that uses a scale.  It also uses a flow meter to meter the carrier.  It is incredibly accurate and I have very little exposure to chemicals.  If I could do it all over  again I'd put it on a 52/53' step deck and probably not go with the center sump tanks.  They are very nice and I get every gallon out of them but they are high profile and expensive.  If I get it out today I'll try to take some pictures.