George:
I shortened mine to 13 ft. then checked it out per the RayMarine manual and found that no adjustment was necessary.
There is a connector kit sold by RayMarine that includes the little flat connector plus pins, which makes life a lot easier during the shortening process. It's way spendy in relation to what you get, but if you call tech support maybe the techie will take pity and get one for you free. (worked for me).
A tool is available which will safely remove the pins from the old connector if you really want to use them but I didn't bother.
The alternative is to haul the cable down to most any good marine electronics repair facility and have them shorten it. (Usually 1 hour labor plus parts).
I'm told it can be shortened to as little as 10 ft. but 13 was perfect for my C-22, giving me maybe a foot extra for a safety factor.
Slipping the connector (sideways) through the radome seal is a little more difficult without that shrink tubing that covers the stock connector but if you wrap a layer of electrical tape around the assembly with the connector sideways then lay on a glob of KY Jelly on the tape, it'll slip through just fine. (The only OTHER use for KY Jelly I've ever run across, btw)
Don
