Images of the real thing;




Judging from the image below & the Sherman cupola below that, they're direct vision ports &, therefore, should be drilled out
horizontally.


EDIT: This is probably why in Vietnam the M48 tank had the cupola raised & placed on a ring of more & larger direct vision blocks. You will, also, note that they got rid of the crappy M85 machine gun from the cupola & welded a mount for a proper M2 machine gun on the cupola.