Seeing as I put a nice hole in my spare head and basically ruined it, I decided to do some experimentation to see the limits of porting. My loss is your gain if you want to take on this job. I'm going to point out the danger areas and the process that I would use in porting the next time.
Here is another thin spot in addition the one I discovered earlier.
Moving on, now to the exhaust ports. When you see that massive divider you will be tempted to shave it down but it is actually hollow.
The roof of the exhaust ports is just as thin as in the intake, so don't dig out that hump in the middle.
Now onto how I will be porting in the future.
Shave down and blend the valve guide support in the intake (this should be the only time to use a carbide burr). Use a ton of sand rolls to just get rid of the rough texture and focus on just blending in the bump and errors in the casting. Thats it. Want a radical port job? Send it to esslinger, otherwise stay simple and use a light touch.