Nats, I'm not sure of the point you're tring to make. The aircraft either will be within weight limits, or it was overloaded. If within weight limits, it has met the requirements for climb performance, in standard atmoshpere. Yes, you might eventualy find a WAT value, at which a sacrifice must be made. This is why people purchse more powerful aircraft, or turbo equipped aircraft - but that would be comparing apples to oranges here.
Fly the plane within limits, it will give you "book" performance. That's what it was certified to do....