"I am not specifically familiar with the 35%+ numbers, "

This is confusing to me

Last sentence of second paragraph of your paper:

"We show that Delta Pointers are effective in detecting arbitrary buffer overflows and, at 35% overhead on SPEC, offer much better performance than competing solutions."

:)

" This only covers metadata management and is not useful on its own, so you need to implement some kind of defense on top of this which is usually costly. The hardware support used by HWAsan only removes masking overhead by having the (ARM) hardware ignore the upper byte of the pointer, which is a nice way to not having to pay for masking."

I'm aware :) There are thoughts and plans here.