What difference does it make with a symmar??

Does anyone have experience with the convertible Symmar lenses?
I have a 150/265 and wonder what difference there is using the back element removed as opposed to removing the front element?

I suppose I would rather keep the shutter/iris protected with the front element if possible?

The difference is:

About one stop less aperture (f:15 instead of f:12)

Longer focal length

More aberration (a LOT more)

Shorter bellows draw

More distortion (quite a bit more)

And you'll be pumping dust into the shutter/iris with the bellows instead of letting it settle (visibly) from the outside.

That much being said, I've used my 240/420 with the rear removed (or rather rear cell in front threads) simply because my camera doesn't have enough bellows to do it correctly.