Bill, this is one of those questions were I do not recall exactly why I did not to what you are asking. It may have been a case of using what I had in front of me instead of running to Tractor Supply and getting 4 bolts. I am prone to use what I have around me at the time unless there is a compelling reason. I know I did not have short bolts of that diameter in my junk box. Now, the bolts that are with the tongue jack are probably serious overkill. If you do not mind drilling smaller holes you could probably get away with smaller bolts, say 5/16ths or 3/8ths. If you are going to the hardware store for shorter bolts, hey why not go with smaller grade 5 or even grade 8 (if the mast breaks that something else is bad wrong). I do not see a reason why you could not go directly to the plate. You are correct, the straps do want to bend if you get too happy with the ugga doogas. I was watching the lock nuts when I bolted this all up. I stopped applying torque after the lock washers had become flat. Anything after that is excessive. Coincidently right around that the straps would start to bow. At that point it was loosing clamping force. I am not convinced the metal in the straps is all that strong. We are talking about a Harbor Freight product.

It is an antenna mount I bought off Amazon in 2020. I can not find the same one now. They have one that is in diamond plate. "Pro Trucker Diamond Plate 1/2 Inch Hole Pickup Truck Box Mount for CB Radio Antenna" The one I used is flat aluminum. I used star washers between the bracket and the bed to get a decent ground. I wanted to spread out the load among a larger area than a traditional mount.