T-Top height. Mine was shortened and I want to extend it

[erebus]

That measurement is to the center, basically above the helmsman's head.

After looking at your pictures more closely, I see what you mean, about the legs. There's a lot more going on there than just the four legs going top to bottom!
Would be more complicated to extend, but I'm not sure any more or less complicated than reconfiguring the feet layout etc. etc.
Guess it depends on your fabricator.