ha ok. I did something similar on my C11. I don't know the internals of your scope or how the rods rest on the back of the mirror but the back of the mirror is not flat, it's very curvy like a bell shape. Couple of things to look for:
1_ focus as best as you can close to the zenith so the mirror sits and rest in a good position with minimum tilt.
2_ while still looking up move your rods to make contact with the glass then lock them in place.
If you push one rod more than the other you're likely to tilt the mirror. If you only lightly touch the glass then the mirror will be supported by three points at 120 degrees. That's the perfect support to hold it in place. No pressure needed.
You're right in saying that pushing the rods too far will get you out of focus. So push them in until you touch something, no further.
Finally your focus will change over time. You can feel if the rods get tighter or looser. If that's the case re adjust them by releasing the pressure of push them in some more.
Those old school scopes are usually very good mechanically and optically so look after it.
PS: here's what it looks like inside of my C11 to give you an idea:
back of mirror:
http://www.astropic.net/astro/C11/ar...w&productid=17
primary cell:
http://www.astropic.net/astro/C11/ar...w&productid=15