No, but highly recommended.
Until a big wind or other force pushes on the TC you will be fine.
I made mine with one sheet of treated plywood. I made the X. Cut in half short-ways, so two 4 foot squares.
Cut slits of the same width as the board is thick (so 3/4 inch wide slits for a 3/4 inch thick plywood).
Cut the slits only half way. The slits are from the center of one edge to the middle.
Put the two slighted boards together to make an X, or T (+).
Make another one of these.
Put under TC.
You can add boards across the top if you like the camper to sit on more than just two X's.
I put the X's on bricks to keep it off the wet concrete.
This takes weight off TC, but you can still have the legs holding up some weight to give TC a wider footprint.
Others have used a couple of saw horses. Yet others have used stacks of shipping pallets. Bricks. Anything works that you can render....
