Spartan Missile,
You should have no problem with the turbine if you leave it where it is, but if you feel you must move it two or three centimetres back it will make virtually no difference to the CG.

Try it and check the CG by suspending the model from the bulkhead right in front of the turbine and you'll find moving it makes so little change to the CG position it has no effect on the XL.

Despite the turbine weight, it is so close to the CG point it hardly moves it. Maybe 3 or 4 MM.

I've tried numerous turbines and moved them fore and aft in my 3 XLs, and that's what I found.
Alan