Really I think it is best just for the spreader. I posted a couple of pics below so you see for yourself, the first is with the spreader fully loaded. The stock hitch on my ranger is only rated for 150#. I have a height adjustable hitch with a triball attachment so I could get the height needed for the spreader. The hitch and spreader empty together weigh around 125#. Loaded prob around 350#s. I have used it a lot this winter with no problems.
As far as trailer towing, I would worry more about lateral movement than the tounge weight. -Keith
As far as trailer towing, I would worry more about lateral movement than the tounge weight. -Keith