"Gary Warner" wrote in message

So, any ideas on how we can do this measure and/or where to
find (buy or rent) scales without spending too much $$$?

1.) I presume you've tried local rental yards, including contractor yards.

2.) You should be able to find a bathroom scale that goes to 280 or 300 for
not much money. Counterweight the aft end of the trailer with known weight
such that you're in the usable range of your scale, then calculate the net
effect on the tongue weight of the removal of the counterweight, based on
tentative wheel position.