CaptainZidgelcorsathe defaults / numbers you stated are a good start. 12 seconds is probably a bit too long though depending on the mapWell it's turbine (queue 1,000 groans). The spawns come out of shutter and garage so the point is like... right outside. I think 9 will do nicely.
If you're doing turbine I would really encourage you to make the spawns farther away from the point and make use of the high ground turbine offers to make it more than a scrunched up baloo. Ultimately, you can't just use turbine. It won't work. You can theme the map to look like and possess some of the turbine traits but a copy and paste will be shit. Keep it in mind you will be making A NEW MAP that looks like turbine, not just cutting out part of turbine and adding a point.