[mr48chev]

I've been in more than one shop that had 2x6 or 8 planks cut so that they could get low cars up enough to swing the hoist arms under lowered rigs.

I've also seen guys have to use similar planks to cut the approach angle on four posts for lowered rigs.

Both have advantages and disadvantages. The 4 posts are great if you have the cross pieces and jacks to raise the car to pull the wheels. Pretty much just for under the car work if you don't. They do work great for increasing parking space though as you can put panels across the hoist so oil doesn't drip on the cars below.

The 2 posts take more care putting the rig on both for balance and for stability but give you a clear run under most of the vehicle.