Hofer’s argument in geometric algebra can be more intuitively given in the conformal model of space and by using coordinate systems less. Also his presentation uses questionable (though probably not uncommon) GA terminology and has at least two ‘shortcuts’ given without explanation. I plan to reformulate, as soon as I figure out one or two things. Well, really, it’s how best to fill in one of those shortcuts.
Meanwhile I have back spasm. Not fun.
On the other hand, the burn on my arm seems to be healing.