Hello,
This is the first time I participate answering a fellow modeller's doubts and I'm more than happy to share some of my still-little experience doing LEED certifications:
Certainly, if your documentation can support the fact that the pre-existing glazing was more than the usual 40% for the baseline case, you'll be able to score those extra points in your simulation. For zone 2A it indeed sounds like the improvement would be pretty big.
I did the modelling for a renovation in zone 3A where the pre-existing glazing was around 60%, unfortunately ,our reviewers considered the plans we had of the old building were incomplete and we were only required to submitt some photos of the old facades for the final aproval.
Just a month
ago we unveiled the plaque so i'ts totally doable, just make sure you send all the complete documentation.
Best of luck!
Mauro Contreras