... it is true that seen from the cockpit, the front turret is on the left, instead of being centered, so should be moved to the center of the windshield ...
I don't know how to do that, but you can try deleting the front gunner like this:
1) In the "Plane/Potez540" folder (not the Cockpit one), open the "hier.him" file (with a text editor, like Windows Notepad for ex)
2) Scroll down to these lines:
[Pilot2_D0]
Mesh Pilot2_D0
Parent Turret1A_D0
Attaching 1 0 0 0 0.173648 -0.984808 0 0.984808 0.173648 0 -0.5 -0.035
CollisionObject xpilot2a
CollisionObject xpilot2b
CollisionObject xhead2
[HMask2_D0]
Mesh HMask2_D0
Parent Pilot2_D0
Hidden
Attaching 0 -0.965926 -0.258817 0 0.258817 -0.965926 1 0 0 -9.99998e-005 0.0911589 0.682725
[Pilot2_D1]
Mesh Pilot2_D1
Parent Turret1A_D0
Hidden
Attaching 1 0 0 0 0.173648 -0.984808 0 0.984808 0.173648 0 -0.5 -0.2
[Pilot3_D0]
Mesh Pilot2H_D0
Parent Turret2A_D0
Attaching 0 0 1 -1 0 0 0 -1 0 -0.1 0.8 0
CollisionObject xpilot2a
CollisionObject xpilot2b
CollisionObject xhead2
[HMask3_D0]
Mesh HMask2H_D0
Parent Pilot3_D0
Hidden
Attaching 0 -0.996195 0.0871525 0 -0.0871525 -0.996195 1 0 0 -5.99995e-005 0.0952604 0.713295
[Pilot3_D1]
Mesh Pilot2H_D1
Parent Turret2A_D0
Hidden
Attaching 0 0 1 -1 0 0 0 -1 0 -0.1 0.8 0
[Pilot1H_D0]
Mesh Pilot3_D0
Parent CF_D0
Attaching 1 0 0 0 1 0 0 0 1 0.35151 -3.72324 0.0396355
[HMask1H_D0]
Mesh HMask3_D0
Parent Pilot1H_D0
Hidden
Attaching 0 -0.984807 -0.17365 0 0.17365 -0.984807 1 0 0 0 0.0952742 0.713352
[Pilot4_D0]
Mesh Pilot3a_D0
Parent TurretExt2_D0
Attaching 0 0 1 -1 0 0 0 -1 0 -0.24 0.3 0
[Pilot4_D1]
Mesh Pilot4_D1
Hidden
Parent TurretExt2_D0
Attaching 0 0 1 -0.34202 0.939693 0 -0.939693 -0.34202 0 0 0.4 0
[HMask4_D0]
Mesh HMask4_D0
Parent Pilot4_D0
Hidden
Attaching 0 -0.588126 -0.317746 0 0.286811 -0.651391 0.817194 0 0 0.031266 -0.301406 0.631831
3) Since we don't know if the front gunner is Pilot 2 or 3 or 4, let's start with Pilot2 (assuming that Pilot1 is the pilot and not a gunner) ...
Delete him by putting a double slash just in front of this line:
[Pilot2_D0] ... like this: //[Pilot2_D0]
4) Save and exit, launch the game and check the result, if all is good, then no need to go any further (except may be also delete the HMask2 line too) ...
... if the front gunner is still "alive", then he is not Pilot2, but may be Pilot 3 or 4, so restore Pilot2 (delete the //) and try the same trick with Pilot3 etc ...
Deleting the front gunner shouldn't prevent his MG to fire on its own, when necessary ...