Well, if you ask for critique, you'll get it from me
The lower horn is unnecessarily long on designs 3 & 4, and they would mostly just be int the way, and present a health hazard, pointy as they are.
The necks look very thin - is the body so wide or are the necks out of scale?
That cutaway at the lower side of the butt, beyond being your personal touch as I see it, adds nothing to the functionality, just makes it harder to sculpt (hard to fit power tools into that corner) and takes up space from the electronics compartment. If you are bent on cutaways, why not put it on the upper side? That way, the offset might also help balance.
Oh, and I'd like to point out that... er... ok, I'll get to the point: they are quite pointy. (pun gallore

)
I know it's up to you to decide, but I think too much pointyness might make it uncomfortable. (Like the thin upper horn resting against your chest or stomach).
If they are b-o, as #3&4 suggest, then the neck pocket might be a bit small.
Aside from all these, nice to see that you are trying to come up with something original, and good luck with your build!
