Getting ready to install the windshield - questions

[Wisconsin_Snake]

I am getting ready to install the windshield, are the marked lines pretty accurate or should I gauge another way where to cut the slots?

If the slots are not accurate, any ideas on how to determine where to cut the slots?

I would just hate to cut the slots and find out they are too back or forward and then have to extend them.

Second, question, are the slots for the defroster good or should I implement something else like defroster bevels

Thanks.