There is almost no room between the turret and the hull on the 1a4. The turret basically sits on the hull. How did you fit the thickness of that bearing race between your gepeard turret and the hull? Did you cut out the bottom of the turret to install it?
On my 1a7 build I glued a styrene strip around the hull ring and then cut the tabs off the turret and glued new ones under to allow it to raise up .010" Worked just fine so far.