Careful with the Gin, that's what will trip you up. <-sarcasm
:sombrero:
I have a device, that while not ideal specifically for tongue weight, does yield usable weights on tires and could be used to get tongue weight. I tried to find a picture of it on the net with no success, so I'll try to describe it.
Picture a square steel tube pedestal with two opposing ears welded on it's top extending above the top of the tube by an inch or so. Then there's a same sized steel tube "beam" that pivots on a bolt stuck through those ears. One end has a little tab welded to it that engages whatever it is to be lifted. The other end has a 1/2" square socket in it and the length of the beam results in a 10:1 ratio between the two sides when a beam type torque wrench is fitted to the socket.
Note that the pedestal is adjustable in height so that the beam stays slightly higher than level when at rest.
In use the tire or tongue is lifted off the ground by pushing down on the torque wrench's handle, a piece of paper is slid under the tire or landing foot/tongue jack, and then the tire or tongue is lowered to the ground. A helper lightly pulls on the paper as you push down on the wrench handle. When the paper slides out you note the 'torque' indicated. Multiply that number by 10 and you have the weight on that tire or tongue.