Scrolling image effect issue

Hi there. Wondered if I might pose a question to you all.... I'm pretty baffled as to what I'm not seeing.

I'm trying to make this animated icon which is basically just a single image being scrolled across in a loop...
Here's what I've got:

I'm using Adobe ImageReady.

I've looked everywhere for a method to do what I've done, but was unable to find anything with the same effect. So I basically just jerry-rigged it myself using two layers... which was the only way I could figure out how.

I like how it turned out well enough. My problem is the size. I've got it set to a GIF 64 no dither with 27 frames. Normally that works for me and is within LJ size specs. This is 130k. I've tried halving the amount of frames to 14 even and am still only able to get it down to 67k. So I'm wondering what the hell I'm missing.

Does it have something to do with how I've made it? Some weird IR quirk? Is there a better method to do this kind of scroll across?

Thanks so much... I will worship you if you can help me. o_O

I've managed to make the animation 37k based on the suggestions by six_two_four  (thank you much)

Here it is now:    

I sized down the original image by 40%, halved the amount of frames to 13, and reduced the colors to 45.
But my original confusion remains, because if you compare this to the userpic I'm using right now, it doesn't make sense. This one is 26 frames and 64 colors. Am I missing something? : /