Hippo Ear Mounting?

I see the hippo ears have a 1/8 inch "platform" on the mounting side. Is the intent to cut a hole in the side window poly for mounting, cut the platform off and mount on top of the poly, or just mount as is on top of the poly?

How far forward/aft is best position for most?

Most builders mount them on top of the window, like Pete above (and me). Usually, the leading edge of the mirror is lined up with the edge of the window.

Mounting them this way make it more difficult to remove the window from the outside, which is arguably a security bonus.
Pete and Will

Thanks. Answers the question and didn’t cross my mind as an option to cut the window like Pete’s. Got to think about that, but it works for Pete