Turret Icons

[Fred77]

I have been playing Steel Panthers since it first came out but have not tried to edit OOBs or graphics before so if I
am trying to do something even Marshal Ney would know not to do I apologize for wasting your time with this post.

I wanted to create several Turreted Forts like the one represented by Icon 570. Specifically I wanted to make Turreted
Forts with Icons 559, 558 and 557. I was hoping to make completely new icons but if not I figured I would
just replace some little used tank icons. I don't play PBEM games and mostly play scenarios I create so no harm.

I decided to test my understanding of how to use ShpEd.exe so I opened Icon0000.shp and replaced the PzKw 35T turret
(image# 21) with the King Tiger turret (image# 17). Renamed bignew.shp to Icon0000.shp and moved to the game's Graphics
folder. Fired up WinSPWW2, started the Editor, purchased some PzKw 35Ts and went to the Deploy screen. Surprise!

There was my new PzKw 35Ts with the new & improved turret BUT the turret wasn't centered on the hull. Huh!?

Out of curiosity I repeated the above process only this time I copied the PzKw 35T turret to bmp, back to shp and replaced
image# 21 with an exact same image. Opened game, purchased yada yada and went to the Deploy screen. Surprise!

There was my PzKw 35T hull with a PzKw 35T turret offset just as with the Tiger turret in my first attempt.

How can replacing an image with an exact copy cause the game to not know how to place it on the screen?

Is there any way to change turreted icons?

Is there any way to create new turreted icons?

And, as long as I have your attention, what is a "shared invisible turret" and why would the game need one,
the whole world wonders?