I read that some M4E2s had a .50 coax. Anybody have a photo of the fit? I assume the barrel must have protruded from the mantle, but how much?

When the M4A3E2 Jumbos were re-armed with 76mm guns in March, 1945. they also received .50 caliber coax machine guns. Any photo of an upgunned Jumbo will show it, and yes, it protruded almost a foot in front of the mantlet.
https://www.google.com/imgres?imgurl=http%3A%2F%2Fmodelhobby.eu%2Fwp-content%2Fuploads%2F2011%2F11%2Fpost-78-1185720798.jpg&imgrefurl=http%3A%2F%2Fforum-console.worldoftanks.com%2Findex.php%3F%2Ftopic%2F59120-jumbo-sherman-m4a3e2-update%2F&docid=m_9aoNrnT89VdM&tbnid=-TuV6wwq2s27NM%3A&vet=10ahUKEwj-vbzw_cflAhXJjFkKHdz3CMcQMwiVASgXMBc..i&w=486&h=327&bih=621&biw=960&q=jumbo%20sherman&ved=0ahUKEwj-vbzw_cflAhXJjFkKHdz3CMcQMwiVASgXMBc&iact=mrc&uact=8

Thanks. I was asking for someone else. Only photos I found of the up gunned E2s were from the right side (76 screening the area out), poor quality shot, or draped with infantry. I'm workng on the tasca kit. Might have to use the spare .50 barrel to make the up grade.

Be mindful that the upgrade used the perforated barrel sleeve b/c the guns were supposedly taken from aircraft MGs (the rate of fire was faster than the ground vehicle version). Don't use the normal .50cal M2 HB (heavy barrel) one.

Secure one of those perforated barrels from the Academy MG set.