Harrison,
A little off the topic of GT40's but your note caught my attention.
In my past life, I was an automobile lift guy - Engineering, Service, Warranty, Product Liability, Manufacturing, Marketing and Sales. Did everything except accounting. My career spanned 45 years in the industry with two of the market leaders. I state this as my qualifications to offer some advice.
The base of the column is designed to sit flat on a surface, not by supports in the four corners. It was always recommended that when a column needed to be shimmed to make it plumb, the area under the column be filled with non-shrinking grout. Right now, you aren't seeing any issues since you don't have any weight on the unit. But once you start to lift a load, the baseplates will begin to bend. The unit will become unstable. Recommend you pack some machine grout under those bases, unless you want the thing to eventually break.
I personally, never liked the concept of un-anchored four-post lifts. They rely on the baseplates deforming until the column itself transmits the load to the concrete surface. The lift wouldn't fall over but in my opinion, wasn't very stable. Anchoring is the right thing to do, but you need to do it correctly or you will create problems for yourself.
Paul