You've got some good talking points, but it could be stronger: "I agree we need more stock available to give new hires." "It seems like you guys are giving up

You've got some good talking points, but it could be stronger: "I agree we need more stock available to give new hires." "It seems like you guys are giving up 10% of your total options which sounds fair to me. I'd like to contribute 10% of my options too. So that gives us a 9% options pool. If it makes more sense to have 12% options then maybe the two of you could each contribute 5.5 points." You could also ask for a salary bump to compensate for the reduced equity.