I say "pentaboxing" because that flows alot better than quintboxing to me.
There is no "right" or "wrong". Penta, hexa and the others aren't exclusivly used for shapes, like some brits like to think.
I use dualboxing, triboxing, quadboxing and then pentaboxing.
So nah, I can't lose this, since 1) you are somewhat wrong in your reasoning and 2) it's a matter of opinion.

Just because you are locked into using "hex" and "penta" as shapes, doesn't mean it's wrong, it's your state of mind that is too narrow.
And since when does Greek and Latin numerical prefixes have anything to do with "the Queens English" ?
10:44:49 < Knapenburger> Dude, I did GCSE English, I was born here, I live here, you are arguing with me, about the Queens English.
And yeah, I'm Norwegian..