The 2021 Weta Marine Sailing Manual has specific recommendations on this topic, section 1.3
California boats bought from the original supplier came with padding already in place. He used 3/8” material cut from yoga mats, I think, 10-11” wide, no cement. It worked quite well over the last 12 years. I am replacing those along with the padding on the bunks of the launching dolly, which has worn down to under 1/8” in places.
I chose 1/2” closed cell foam ordered from Home Depot (it’s a neoprene/SBR blend, the latter is helpful for abrasion resistance, and only serious geeks want to know it stands for styrene butadiene rubber). It came in a 39 x 78 inch sheet, enough for the tramp pads, the bunks, and material left over for another set of bunk pads for somebody else. The bunk pads are doubled (1” thick) under the main hull since that’s where the pressure is. Cutting this stuff into strips neatly was done by using a super-sharp knife (resharpening it after every 78” pass, this stuff dulls even top quality blades very rapidly) with a wooden board as a guide. Don’t try using that old box cutter blade.
I used 10” wide strips for the tramp beams, no cement, wrapped around the beam. The lacing holds it in place in a bombproof fashion, the 10” width means it won’t shift out of place, and the outer edge is padded. That’s good when your heinie is out on the ama. This stuff is tricky to glue, I had poor results with contact cement on the complex shapes of the bunks and ended up with Gorilla Glue (polyurethane). Wear gloves and read the instructions, the non-foaming version is neater to use. When re-lacing the tramps, wrap the ends of the cord with some duct tape, shrink tubing or whip them to make it easier to push through the webbing loops.
So, there is more than one way to skin this cat.
Does anyone know how long the square member is? My Weta is a two-hour round trip away right now, but the stores I need to buy padding at are here!