I've used the CCS system for years. But, embarrassingly haven't done any CCF tests.
So, today I decided I would give it a try. Went well overall.
However, I tested an dancraft GXT that came up with a CCF of 85. Then I took the off the tip and wrapped on a single foot guide, which when weighed on my digital scale is 1/2 the weight of the tip. So, I assumed a bit of an increase in the CCF number. But, it came out as 83. Not a huge difference. But, not what I expected. Did I do something wrong or was my assumption in error?

The CCF should fall as you add more weight to the rod, particularly near or on the tip. For the time being let's assume you did everything per spec.

You say you took off the "tip." Did you have a standard tube type tip on there when you did the original measurment?

Something else comes to mine - did you weigh the thread and any finish when you added the single foot?

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It was a Minima tip with a little thread and finish. I removed that and wrapped a Minima titanium single foot on the top with no finish. So, definitely thought it would increase the number.
The guide weighs 1/2 the tip. I wouldn't think the thread would add that 1/2 plus some to change the number. I don't know. I'll try it all over tomorrow.

Hard to say but one thing we can be certain of is the laws of physics didn't change, so something is amiss if the single foot and thread actually weigh less than the standard tube tip.

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I think I figured out what I did. Operator error. Like you said, physics hasn't changed.
On the first setup with tip I think I mistakenly counted a full oscillation on the up tick instead of a full oscillation being completed on the down. Which I did correctly on the second try with guide as tip. That would have been less time on the stopwatch and produced a higher number. We'll give it another try.

I just re-tested with the Minima tip and it was a bit slower. It came in at an 82.5. Not as much of a difference than I was thinking.
I think it shows that, for this rod anyway, that extra tip weight (about .2 grams) doesn't have as much impact as I thought.
This is a finished rod by the way.

If the rod is fairly stiff and crisp, then that little weight might not make much difference. On a lighter rod, it would make more difference.

Have you tried the measurement with no tip at all? Just out of curiosity.

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No I didn't. But, good idea. I'll give it a try.