This sticky can't be done without pics and thread links to excellent home made Excal shafts and such, along with a few other tips and other products sold by Findmall sponsors for the Excal...
Plugger Shafts (found at Findmall sponsors) for water hunting, pros and cons of behind the elbow control pod mounting, flipping the control pod backwards in that position for easier access, homemade shafts, etc, walking canes that already have an arm cup and grip for perfect easy/light shafts like they were meant for detectors, walking canes that break down into 3 pieces or so for travel shafts (Findmall sponsors sell Plugger's version of these too as well as Andersons), etc.
If you go the homemade route walking canes and even ones that break down can usually be found dirt cheap at Goodwill stores used, but many opt to build homemade shafts with blank aluminum stock or even carbon blanks, which are cheap if you know where to look. Heard of some guys using fiberglass tool handles for broom or paint rollers and such from home improvement stores too that work well. I found when I built my homemade light shaft that the inner extending aluminum pole from an Unger (or Etore) window cleaning pole at home improvement stores (these are professional grade) was perfect for my upper shaft on my GT light weight shaft build. A much lighter grade of aluminum than stock to save more weight, but that might be too light a grade for the drag stress in water hunting?
http://www.findmall.com/read.php?21,1286886,page=1
http://www.findmall.com/read.php?21,1242922,1242922#msg-1242922
http://www.findmall.com/read.php?21,372849,375081#msg-375081
Fixing the lower shaft coil mount plastic insert if it comes loose, & Plugger bolted camlocks to take the slop out of the shaft. Very important for water hunters or the play could get worse over time due to drag. Any play in the shaft is a bad thing, but even worse in water hunting due to the drag...
http://www.findmall.com/read.php?21,1346303,page=1
Some pics below of homemade or commercial aftermarket shafts, bicycle end bars found at any bike shop for grips (you can also cut them shorter and you can put rubber grip covers over them for excellent comfort). Notice the mount high behind the elbow to lesson drag too on these. You can buy Plugger or Anderson extensions from Findmall sponsors that will even go on the back of the stock shaft to do this, or just build a longer shaft if you are making one.
Many ways to go about custom shafts for the GT or Excal, built by yourself from scratch (easy) or bought and customized from Findmall sponsors. Possibilities are endless, and people do what works for them.
[size=large]Just remember the things to be considered when buying or building one....comfort, balance, lessening drag, and easy access to your controls. If you are using the stock shaft setup on an Excal what is wrong with you man?[/size] 
It has no balance whatsoever and even in the water is not friendly to human posture. At least put an extension on the back, mount the pod back there, and get the balance and drag down for you, but I still don't like the S-shaft on those things. Just not user friendly.