I may have misunderstood how it works then. I thought that merged mining meant the miners work on both BTC and NMC.
I want my miners to work solely on BTC.
You don't take some of your compute power away from BTC and into NMC. With the same computation you solve both BTC and NMC blocks. That's why it's called "merged mining". You get the same BTC and bonus NMC, which is why everyone is excited about it.
For a technical explanation of how it works you can read
this stackexchange answer.