There is a way around the sill welding problem with my two poster.
Mine was designed for Porsche repairs, each post is offset, so you have almost full access to the length of each sill.
In other words the drivers side post is next to the rear passenger door (C pillar), the nearside post is at the passenger side A pillar.
The arms are of two different lengths on each side.
Hydraulic lines connect two rams, there is nothing on the floor between the posts, everything goes overhead.
This is the only two post of this design I have ever seen.
The only other interesting design I have seen recently is a single post side lift , that gave fantastic access for sills .
For domestic use an end lift of the type used in Chelsea garages would be good as it doubles your parking area as well as being very narrow.
Mrcheerful