Here is the bench that I made back in 1998. The top is 1" UHMW (I think that's right, cutting board material), the legs are stainless square tubing. The seat came from the center piece I cut out of the top. I used a router on the edges and counter sunk the stainelss bolts.
It weights about 50lbs and can be "rolled" into the back of a full size p/u. I used to do this and set up on groundhog fields in VA.
The first summer I used it, back in N.C., I drilled a 2" hole in the center of the top so I cut fit a patio style umbrella in it. I soon figured out I'd have to endure the sun/heat if I wanted my bench to be steady in the wind. The umbrella caused a lot of unnecessary movement.
All the legs are adjustable, as is the seat, but I haven't used this feature much because I built it for me.
This thing has been tough. It's been backed over by my oldest son. Scratched the crap outta my wifes Grand Prix. Man, she was hot!
One time it slid out of the back of my truck and skidded down the road for a long ways. I was running 55-60MPH.
It's been to three different states with me, still here we are. JohnnyK.