if you are making a plasma table and simply wish to only cut 5mm

[Robin Hewitt]

If you always start at an edge you don't need to back off to pierce height.

If your torch rests on the surrounding plate and has a crude mechanism to back it off to pierce height you can cut any thickness.

Torch height control is usually for people who think they can make a perfectly flat bed using welding irons and cheap box section, then discover they cannot.