Just a suggestion after seeing your concerns and the other post regarding the car rolling, falling, jack stands, chocking and stuff. You might want to try my wooden cribbing method. That is to go to home depot and buy two 8 feet long 6x6 treated lumbers ($40). Cut them into one foot sections and working around the car, stack them three high placing them at the OEM jack locations. The car will be a foot and a half off the ground giving you plenty of clearance to work comfortably under it and the car will be solid as a rock. You get plenty of room to work and roll around on the creeper because the jack stands are completely out of the way. Of course you don't need to do this for things like changing the oil and stuff but it's great for doing things like you just did.