What about trying a slower paper? A lot of regular RC papers seem pretty fast, but there are other options, such as warm tone, which should be slower? Of course if you like the paper you are using, don't change it, but the paper could be a factor too?
Makes sense as Cyan in minus red only which has no effect on a blue sensitive paper.
Originally Posted by ic-racer
To OP: have you checked your lens, does the apperure close when you turn the apperture ring?
Print bigger ;)
Extra cyan does practically nothing as stated above, but dialing in more of both magenta and yellow will slow the exposure and allow you to keep the same contrast. You can also put an ND filter on the enlarger lens or sometimes in the enlarger (e.g. if it has a filter drawer).
And don't be afraid of the f/16; the diffraction should not be visible to the eye in an 8x10 print and you can verify that yourself pretty easily.
Are you using the older color head with the power supply, or the solid state s version? I am using the s version, with 81M and 71Y of filtration for grade 2 on arista paper ( I might have those backwards). This gives me an exposure of 15 seconds when going from 35mm to 8 x 10. Lens is about f5.6. Also, I use the condensor for B&W. I assume you are using B&W. When I tried the condensor with RA-4, I had exposure times of 5 to 7 seconds, and too much contrast, so I use the diffuser with RA-4.
I have a two stop ND filter that I put under the lens when the speeds get too short. A polarizer works just as well.