One is short the other is not!
The long is better suited to those not planning on using a fisheye lens.
Yes there is a 4.5cm height measurement difference between the TCPShort and the TCP.
Both measurements are from the base of the rotator to the top of the bracket.
The TCP vertical bracket is 33.5cm tall
The TCPshort vertical bracket is 29.0cm tall
Mate, $250 for the Kaidan upgrade is ridiculous. Contact NinjaBill and buy a NN3 it will handle the 350D and Sigma no problem. If you want more strength then the Agnos MrotatorTCPS is a better bet. Bill offers a money back guarantee so you have nothing to lose. Wack the Kaidan head on ebay and get back as much as you can.
Mirror ball in my opinion are a poor gimmick for those who cannot patch or stitch correctly. 9 times out of 10 they look very out of place and ridiculous introduction to the scene. You either should patch the area or add a tripod cap with something of merit like yours or the client information. (it is MY opinion)
Sky caps are horrid and should be avoided at all costs. Cleaning up the "star" in Photoshop is pretty easy and is something that should be learnt (or "learned" as you yanks would say).
Most if not all Vignetting can be dealt with using Photoshop CS2 RAW converter.
I would just fix the star in what ever photoeditor you use... all it is a dark area all across the top of the image, probably top 15 pixels or so. Clone it out removes the star.
Another way is to use photoshop FILTER | OTHER | OFFSET. Make sure the auto wrap is box is checked. Then rotate the image VERTICAL down using a -15 for down 15 pixels. This offsets the image upward so it wraps around to the bottom where your tripod cap is located. It does not remove the star.. it justs moves the image so that the star is now wrapped into the bottom area.
I assume you are going to fix the tripod cap anyway with some advertising logo.