Unless you can specify the brand and characteristics of the chassis you get what the coach manufacturer orders by the gross. (Unless you buy a coach with a custom built chassis but you are not talking about any of the general manufacturers.)
It would be great to be able to design and order the chassis for your particular needs but that would require the dealer to be able to "coach" each buyer through the design phase. I wonder if even the top end custom manufacturers go to that level of detail when building a coach for the buyer?
It appears that each manufacturer goes through a design stage for each model where they specify a general chassis design which includes axle capacities and everything is built on that bulk order. I suspect they may build several models on the same chassis to get the best price from the chassis manufacturer.
It appears that every once in a while the coach manufacturer will cut the design a bit too tight and build a line on a chassis that is marginal. Generally there will be a recall of that error in design.
I expect that even Spartan (only builds upper end) chassis have been placed under coaches that have come close to the limits. It is not the chassis manufacturer who is responsible for overloading the chassis. It is the coach manufacturer who estimated the amount of weight they would be placing on the chassis.
Gordon and Janet
Tour 42QD/inTech Stacker