What there is also is this wisdom from Rick Fielding. One of the many jewels he left us............

Subject: RE: Capo - what are the rules?
From: Rick Fielding - PM
Date: 16 Dec 00 - 10:46 PM

Just a bit of background on the "grooved capos" for anyone who might be interested.
I've always loved the 12 string guitar, and have owned at last count 18 of the suckers. Everything from Stellas through Martins, Epiphones, Guilds (several) to my current (and all time favourite) a Big 20 year old Takamine. Being a Leadbelly fanatic, I usually tuned them down to C or even Bb or B. I've always used quite heavy strings (for the last ten years I've used a custom set from Connecticut that has a 68(!) on the bass.)

Right from day one I found that normal capos just couldn't hold down the strings without distorting some, and since I'm a tuning fanatic, I started buying every capo I saw. I'm probably older than you Mooh, so you still have time to catch up to my 50 or so.(I know..there are stupider hobbies than capo collecting but try telling that to your wife!)

One day about twenty five years ago I cut a small "V" in the rubber of a Bill Russell and noticed an immediate difference. The big bass string simply wasn't being stretched as far as before, so I had one less string to retune when the capo was on. Needless to say I've butchered dozens of rubbers on various capos trying to get a perfect fit for whatever guitar I was using, but it was challenging and fun.

Today I use a Golden Gate capo with a piece of floor tile replacing the original rubber. I've cut four very small "v"s under the four "big" strings, and it works best on the second to fourth fret. Rarely do I have to retune, and it makes it soooo much easier to play with others and not be slightly sharp.

You can do the same thing on a Shubb. The rubber they use is just about right. Dunlop "C" clamps are good too...and cheap.

Rick