Canadian Centurion tanks question

[Dan Martel]

All this Centurion talk got me to take another look at my copy of Don Dingwall's The Centurion in Canadian Service (2005) and noticed this quote:

"When the 105mm gun was installed in Centurions, regardless of nationality, the loader's hatch had to be turned 180 degrees and moved to the extreme outside edge of the turret roof, as the recoil of the L7 gun would almost certainly have removed the lower legs of the loader, even though the breech assemblies of the 20 pounder and the 105mm guns were virtually identical in size."

Two questions. First, how does one move a hatch on a tank turret roof? Cutting a new place for the hatch is one thing, but how do you fill in the space where the hatch once was? It's the "how do you fill in the turret escape hatch at the rear of the turret" problem all over again.

Second, wouldn't the loader be sitting inside the turret assisting the gunner during the operation of the gun, rather than standing half out of the turret waiting to lose his legs?

Once again, I turn to those with superior Centurion knowledge to me to answer my questions. How does one move a turret hatch and where is the loader during the operation of the 105mm gun.

Thank you, gentlemen,
Dan.