LOL actually that's how mine came. Yeah the thumb button screws onto the shaft and is secured by means of a tiny set screw; thus you can change the angle of the thumb button. So looking at the third pic
@Red Beard posted you could rotate the thumb button on the shaft/post so it's sitting at more of an angle. I might back mine out a bit more as I have pretty wide hands. No, it doesn't come with any other shafts/posts but if you were careful you might be able to machine so more threads onto the included shaft and then cut some off to make it shorter.
Here's a couple more pics showing how it fits in my hand. I have the button pegged all the way to the rear as I like it buried in the web of my hand.
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