Ordering F-350 7.3 CCLB SRW - how big of camper can I get?

You will only discover "incurable weight limitations" if you intentionally buy a camper that's too heavy and are too stubborn to make the compromise, i.e. buy a smaller/lighter camper.

High 4000's are a bit much for an SRW, I agree, but we're not talking about high 4000's. We're talking low 4000's. Getting up there, but still manageable.

Heck even 5000 is possible with an SRW if you throw enough money at it.