API 610 only says that allowable nozzle shall not over the Table.5

Annex.F gives you the equation that you can combined acting force&moment at the pump in&outlet nozzle, by combining the force&moments, factor 2 will be used for checking each nozzle and combined nozzle(see F.1.2-a,b). But the standard states that this method can result misalignment, and using Annex.F should be informed to owner and vendor.

So before using Annex.F, owner and Vendor should agree that you can use Annex.F to evaluate the nozzle loads.

Also, Annex.F is not exactly let you use 2 times of allowables. If you have a look at the Annex.F, it only gives you the combining equation simillar to turbine alignment check evaluation.