OK. Here goes!
I laid out the arms and weapons as follows:
L = Left arm; R = Right arm; G = Gun (obviously)
I kinda goofed when I was setting this up: "Left" arm is the arm on the left side of the picture, not his actual left arm (8 years of university, you'd think I'd get that straight

)

#1: L1R1G1: Nice pose:

#2: L1R1G2: Again, nice pose, with rifle:

#3: L1R2G1: Looking good:

#4: L1R2G2: Not bad, but rifle is a little long for the hand to support it there:

#5: L1R3G1: Pretty good: "Come here, you rebel scum"

#6: L1R3G2: Now with rifle: "I said come here!!"

#7: L2R1G1: Onto a new "left" arm that has a sharper angle at the elbow:

#8: L2R1G2: I like this pose a lot better with the rifle as shown here:

#9: L2R2G1: These two poses really don't work - his "right" arm isn't supporting anything:

#10: L2R2G2: Again, doesn't work (unless he's saying "I want that $50 you owe me"):

#11: L2R3G1: Not bad:

#12: L2R3G2: Seems better with the rifle again:

#13: L3R1G1: And onto the third "left" arm, this one looks awkward with his "right" arm down and the "left" one aiming:

#14: L3R1G2: This one looks worse with the rifle, very awkward:

#15: L3R2G1: These 2 don't work either (..."can't reach that itch..."):

#16: L3R2G2: Again, just goofy:

#17: L3R3G1: Better, but the blaster is too short here for his "right" arm to support it:

#18: L3R3G2: MUCH better, one of the best poses, but I should have rotated his head so it looks like he's aiming:

So after all that, some of the potential poses just don't look right (or plain stupid, but I think it's pretty obvious that Gentle Giant didn't intend for all of them to be used).

When you set up the 6 troopers that they show on the side of the box (Squad 1 and Squad 2), you can really only set up 2 more poses with the 9th being pretty much useless. But the 8 Stormies look pretty cool as a squadron:
