I use the plastic pads, have used solid wood (thick plywood sounds like a good idea). I have had the solid wood (2X4, 4x4, 2x8) spit down the grain of the wood. The plastics have their problems and their plusses. I have found the plastic ones to crack and break, especially on gravel, which can be an uneven base for them. I have had them slide instead of roll under the tires on smooth concrete or smooth asphalt. I have had them sink into soft semi-mud ground, and be real fun to get them unstuck. On the other hand there is no labor involved in making them, they are available at WalMart, they are uniform in size, and stack nicely for storage or getting higher lift. I think I may look into some marine plywood pieces to augment the plastic in situations that call for it.