Rear intakes on midship mount pumpers quite often outperform front intakes simply because of their design and "easy" path to the fire pump. When specifying a rear intake it is important to include the size of the pipe used. In some cases, just saying that you want a 6-inch rear intake will get you 5-inch pipe to the pump and a 5"x6" adaptor for hose connection. Of course, going to 6-inch pipe is increased cost, but compared to the flow capability under drafting conditions of a front-intake, the cost is generally worth it.
During our October seminar in Pike Road, Alabama we came across a really nice 1500gpm/1500gal engine tanker made by KME for the Pike Road FD. The rig had many nice features, one of which was the 6-inch (with 6-inch pipe) rear intake which we used under drafting conditions during the 2-hr drill. As with anything, it is the "little-things" that make a difference. Carefully review all of specifications and try to use performance specifications wherever possible.