There's no way to set a max shipping weight for each carrier at this time. Allmoxy offers a variety of shipping options and customers are able to select different options when ordering to find the most economical choice. We also recommend that the staff member in charge of verifying orders review the shipping option selected and make sure that it is feasible.
When you set the max weight per package in the shipping settings (let's say 50 lbs which is standard), you're telling Allmoxy to break the order up into x amount of 50 pound package. If a customer tried to order 2000lbs to be shipped ground, it will calculate pricing for FORTY 50 pound package, which will be astronomical compared to freight shipping. So typically the customer will find the best shipping option for their order, but a staff member reviewing the order & shipping preferences before verifying would catch any mistakes.