I built a small T shaped one using table legs like yours, and in the fields I shoot a little wiggling settles the 4 legs in well. I was concerned about the 4 vs 3, until I built one.
My T is more of a pie wedge, the front is curved, it is wide and the back portion is skinny so my elbow usually hangs off the benchtop, but when it is on it, after 100+ rounds, I usually spend more time making sure the red elbow is off the bench the rest of the day's shooting. The narrow back and wide front lets me slide my front rest maybe 30 degree's right-left, and if I see a bugger off to the side I can move the chair, move the rest/ rear bag in close ( or ditch the rear bag) and swing wide, and re-adjust the whole setup if I spy more vermin I hadn't seen sneaking around.
Another week and a few days and I'll try mine out again for a week of shooting Skippy, the flying squirrel.
That 4 leg sure is stout!!!!!
Allen
