Mas response -
"I agree with you that it's best to keep both eyes open.
If your modified Weaver stance is the variation with gun arm locked out and support arm bent, also known as the Chapman stance, bring your chin to your gun arm bicep and the opposite eye will be directly in line with the dominant hand. No reason not to be using your dominant eye just because you're cross dominant."
Tried it today at the range and it works as advertised.
That's Mas for you - LOL!