T337G: Inner Side Windows

[basloane]

I own a 1974 T337G. I am in the process of upgrading my interior and want to replace the inner side windows with new clear plastic. Of the total of 8 windows, 6 are .080 thick. The second and third windows ( numbered from the front ) on the right side are .187 thick.
Does anybody know why these two inner windows are thicker? Is anyone aware of a reason why I cannot use .080?
Thanks,.....