I use 6 ton stands, they hold the car up 24". When I want to go higher I put them on blocks 4"X16"X16", If I need to go higher I use 6"X16"X16". If the car isn't going to tip with the stands on the floor it isn't going to tip with the stands on the blocks. Probably be a lot easier to tip if the blocks were the same width as the stand. Problem with having the stands on blocks that wide is getting around between the blocks.