What is your model?
Welding is not my field of expertise. For as long as you can present a steady and known-quantity load to the generator, you should be able to dial in the overload setting. Popular choice is to use several space heaters as a load bank. They have a power factor of 1 (resistive) so you know that the kVA and kW are the same.Can a welding transformer be used as a 5 kw load bank to set the overload protection ?