I am incredibly paranoid about such things. Not sure I would feel secure with the method you are describing. A couple years ago I tried my hand at masonry in my basement by sealing up an old window opening with cinder blocks. This entailed spliting a few for the half pieces on the ends. Some were real tough, some remarkably not so. I use jack stands plus pieces of unsplit wood(cylinder shaped) as backup and hell if I have the tires off...they go under too!
Aint goin out like that!