Hi Tim , not trying to divert you off your chosen course. Just to fill out the options for the decals contained in the HB kit. Here is a pix with what I believe are the decals # 4,5,6 & 11 and it would seem its for a Hexagonal turret!!!!!!
On a friendly constructive observational note if you are open to it and its not too late there is a slight seam visible on the rear of the turret in one of the photos you posted .. where the two half turrets parts join. You could remedy that with either some TLC or just cover it up with some type of tarp. The model looks the part and you have put a lot of work into it. Looking forward to seeing the finished article in due course