If the Cannon's movement is visibly impeded by adjacent hull parts, then filing for relief might be an option. The amount of elevation will also depend on how far the gun mechanism can travel into the lower hull space. If it's already almost touching bits in there (like the MFU, for example), then creating more elevation would be counterproductive.
Another idea is to compare the elevation (and depression) of your gun with this one:
This tank is using a Clark controller with a custom elevation/recoil unit. Perhaps you could consider that option, if you're unhappy with the current lift. How much is it supposed to elevate in reality? (actual Leopard)
It was something like -9 to +20 degrees on the first Leopard 2. Not sure about the 2A6
https://www.thingiverse.com/thing:2103220
"Get your facts first, and then you can distort them as much as you please"- Mark Twain.