I think CFS is very lucky it hasn't been caught out with trucks that can't boost effectively, it might be alright in some areas but where I come from we have often had the 24P fail to boost, and yes we know what we are doing, we simply can't flow enough of the wet stuff, I still shake my head at the fact they only spec'd 2 inlets and 2 outlets. Most pumpers around the world are nearer the 1000GPM mark, but I guess the key is, if you can flow enough water 500 GPM will do an alright job, its just that what CFS builds restricts the flow.
As most have said, your Stirling, Mt Barker type trucks are your true pumpers, although Stirlings (as has been said many times) could use a high pressure stage,but you know how it is, when people mess with the specs you get a truck that doesn't work.........