Hi Simoncnx,
I'm not sure if you've done this yet, but some people have mentioned it in previous posts so I'll bring it up again, try using the floc method to dial in your rennet amount. It might be easier to do this with a smaller batch, say 10 litres, then just scale it up. Anyway, if you've read up on how to do this, skip this post, if not, give it a go.
First, you will need a small light plastic bowl (i.e. a small container you might put a baby's food in). At the time you add your rennet, float this bowl on the milk (cleaned and sterlise the bowl, and the baby while you're at it) and write down the time. The bowl will float around at the gentlest of touches. Each minute, tap the bowl, it will float freely. Eventually, though, it will start to get a bit sluggish, and it will move more slowly. Start tapping every 30 seconds once it's clear that the boat is getting clogged down. It will act like the anchor is dragging, or like walking through a swamp. The milk will be trying to hold the bowl rather than float it. Eventually, a light tap will not move the bowl from it's place, rather it will sort of lurch forward and get pulled back. Write the time down when that happens.
This point, when the bowl is "stuck" is the flocculation point. If you're using the right amount of rennet, then the time between adding the rennet and the flocculation point should be somewhere between 10 and 15 minutes. If you reach that point sooner, use less rennet next time, if you reach it later, use more. Keep adjusting until you've got the milk and rennet working together to get you a floc time of 10-15 minutes. Shouldn't take many attempts.
Let's say you've found it required 12 minutes to get to the floc point. You can then use this value to determine the time at which to cut your curds by using a floc multiplier. For Cam, that value is in the 5-6 range, so let's go with 5. 5 x 12 gives you 60 minutes. That means, you should cut the curds 60 minutes after adding the rennet (remember, you've used 12 of those minutes already just getting to the floc point).
Since the milk varies from season to season, and what the animals are feeding on can influence things, using the floc time to detemine the cutting time results in more consistency between makes than using a constant time.
Now, as for the ratio of geo to PC, I'll leave that to those who are more experienced with this kind of cheese.
Good luck, and let us know how it goes for you.
- Jeff