I used 2x6 for the legs to resist side to side movement and the base for more contact . The base also helps the legs from spreading. All the angles I used were 15 degress due to the height (overall is 29"). If yours is shorter the angle should be greater for more leg spread (though this is the weak part-so minimize this). Originally I was going for 22.5 but was also going to put in center legs straight down. (our camper is 4000lbs) Then realized with the height 15 would work with less spread and no need for center leg but still have enough spread to resist front to back rocking.
I did make the angle cuts on the 2x4 under the top 2x6 so the legs had a flat surface to set against. I only cut back width of legs. I also put the tie brace behind because I let the leg brace into the leg, mostly for looks but I think this captures the legs better. I ran bolts thru the tie brace into the legs and bolted the legs thru the top 2x4. So the way Im looking at it there safe (metal would have been stronger but much heavier). I put full weight of camper on it, zero rock! and I tried. I will still use jacks! but most of the weight is on stand. Still wont jump in the bed when she's off the truck but Ill feel better when its sitting in the driveway. (Maybe a nose stand???)
I still may add full plywood sides to the legs. In looking at design, especially if spread is larger, all the weight of the camper will try to push the legs out. Assembled all joints with profuse amounts of Elmers glue and 3" screws. Hardest part was drilling thru both sides for 6" top bolts. I used agar bit to counter bore so nuts/washers would sit flat. Ive since built back one which is 4" shorter and painted them. Note- I made the back one 4" shorter, but when I went to put under camper realized I could not set it all the way to back edge. There's a cut out access panel in the floor of our camper at the rear corner, if the camper were lowered not flat with the support or the camper rocked toward that corner could be a problem. So I had to place it about 16" toward the front-so it was about 3/4" too short.
So if you've a notion a saturday and 30 bucks you too....Just another idea.
Materials (for 1): pressure treated (2)2x6x8' (2)2x4x8' (8)5/16" x 3 1/2 all thread carriage bolts (2)3/8x 6 bolts & (1/2#)3" screws, drilled pilot holes.
Top is 2x6x4' with notched 2x4 screwed under neath. 2x6 legs notched to accept 2x4 brace, tie brace bolted to legs butting against leg brace. Screws tieing everything to each other, not shown screws from top & base going into legs
