Ewwww...... Please, please never get under your car with only floor jacks. The whole purpose for using jack stands are as a safety measure in the event that the floor jacks fail, and they do. Many people have died getting under a car with floor jacks. DON'T DO IT!

Best case, you will cause serious damage to your car if one or more of them fail, or a chain reaction happens if one fails. IMO, you did not solve your problem.

P.S. I would never trust lifting my baby with a $27 floor jack. Lots of potential for very bad things to happen.