Here is a picture of my M4A3E2 "Jumbo" you can get a good idea of the glacis thickness by looking at the keyhole cut for the bow gun, as well as how much thicker it is than a non-jumbo differential which is installed in this case so we could throw tracks on it and have it sit for static display until we get around to it's restoration...it is #73 of 254 built, one of only 6 or seven left in the world, and I am sure the only one in Canada.
Regarding headlights, the original glacis under the extra armor plate has no holes for headlights either, some Jumbo's do have the headlight holes under the armor plate...some don't...very odd