brains613
Flush
Not sure how precise you are intending to be, but if you're using a 1/2" bit or 1/4" bit, remember to factor this in when calculating your measurements. I personally, do my arc measurements (drawing the exact arc onto the surface), and then simply adjust my jig distance so my bit falls just outside of the line.
Some people will chuck a small pencil into their router, instead of a bit. Then run it across the cut. This will show you where the bit will go. It's certainly not bad practice to do that.