I believe the RT payload is like 1,200lb. You should be fine. Even if it's a softer spring rate I doubt they'd make it so soft it reduces capacity by 50%. And if you bottom out it isn't even a big deal, there's bumpers that take the impact. You should be fine though. And if you load it as close to the cab as possible more weight will be up front...
Breathing in and out is good enough for me.