Digiscoping with Canon Powershot SD4000 IS OR Sony DSC TX 1

Hello all,
I'm excited as I wait for the delivery of my new Nikon Fieldscope ED50A, and I'm researching a lot on the camera I will need to go with it. I have a Canon Powershot SX10IS, which I'm told is not good for this purpose due to it's high optical zoom.

So, I've basically narrowed down the choices to these two cameras - the Canon SD4000IS, or one of the Sony DSC TX series (1,5, etc). I'm looking for a camera with a good burst mode (preferably more than 3-4/sec, mostly for action/sports photography). Having a live histogram preview would be a good bonus. It seems to me that the Sony DSC scores over the Canon SD4000 in this. I've read that internal lenses are better than external zooms, so again the Sony series scores over the Canon model mentioned above. I'm a bit concerned that the Sony (TX1) has an optical zoom of 4x, which I'm told is the upper limit permissible, before you start getting vignetting.

Has someone out there tried digiscoping with the Sony DSC TX series?
Any opinions on the above would be welcome!
Thanks.