Welcome to the DS family and forum.
First, the 9" and 1" measurements you referenced are Maximums. You may put the pivot closer than 9" and lower in the water than 1" above the extended hull line. ( See DaySailer Association tab, Handbook, section 3 rules 6.5 and 6.6, i think)
I builit my rudder to be very close to the transom so my pivot is about 6 1/4" from the transom, and about 1/2" above the hull line. Our rudder is small enough and looses area very fast when you heel up, so I wanted as much blade in the water as possible. Also, by not pushing the limits, I have no measurement hassles when measuring.
As for angle, best preformance will probably be straight down. When you angle it up, the weather helm gets very strong.
Hope this helps. and happy DS'n