While the actual meaning of Boxing day has less to do with Boxing than I think it should, that's no reason not to blog about Boxing.
Re-reading the Boxing style - and the box "The Sweet Science" from GURPS Martial Arts, p. 152-153, what would I change?
Writeup: I think the writeup is solid. Nothing really leaps out at me as something that needs changing. It's still accurate and engagingly written. The tough part is the Art, Sport, combat skill split - Boxing really does need both Boxing Sport and Boxing, but it's not like you learn one without the other. I've yet to meet a proper boxing trainer who will teach you to fight without requiring hard contact in both directions. Stay on your toes and move quickly or the focus mitt will find its way past your guard and onto your face.
It would have been nice to write it in light of the fighter between Mayweather and McGregor (highlighting expert specialist vs. expert generalist in a specialist contest) and the growth of bare-knuckle fighting again.
Additions: If I had to add anything, I'd add Targeted Attack (Boxing Punch/Vitals) for those liver-hunting left hookers that I know. I'd probably add a box somewhere - for fighters in general - with some disadvantages to reflect TBI (traumatic brain injury) and the cumulative effect of head blows on personality. It's not just lost IQ and lowered Appearance.
Removals: Although I very much like the Uppercut technique (also useful for shovel hooks!) if I had to cut something I'd cut that entirely and cut it from Boxing. It's not something that necessarily needs its own rules. It doesn't need cutting, but it could be cut and leave the style usefully intact.
Overall, I think we did a good job on all three versions of Boxing - modern, Ancient Greek, and Bare-Knuckle.