You said, "Rick, thanks for all the info. This forum has been great. Lots of good info. from sailers who apparently know and love sailing. I'll get the measurement info to you soon to see what you can put together. I'm still haven't decided on the course of action (spinnaker vs hooter), FX-1 Tony seemes to have put together a pretty slick spinnaker snuffer system. I am becoming a bit concerned about the possibility of mast breakage (a topic that has come up several times) and would like to know your insights. "

We also sell spinnakers, but sincerely do not think that would be the best sail for what you want to do.
Your call, that is for sure.

Most folks have been placing the halyard turning block higher and higher up the mast above the hounds. The higher you go, the more likely you will break a mast.
The way you keep from breaking the mast is with mainsheet tension -- this acts similarly as a backstay. Some very seasoned sailors have broken masts simply because the mainsheet slipped out of the cleat.., and Whammo!
On my Taipan 5.7 my son and a friend were sailing the Hogsbreath-Keys 100 and were doing well. They kept the main sheeted and played the traveler in the puffs. One puff hit and helmsman allowed the traveler sheet to slip from his hands -- the traveler flew across the track and banged to a stop at the end. That was just enough for the mast to break.

When we first started putting large headsails on cats we were very conservative.., around 30" above the hounds, but folks kept moving the point higher and higher. Soon they were very close to the top of the mast.

In one way, higher is better. It opens the slot more and allows more sail area, particularly the leading edge. The bad news is you are taking a chance on breakage.

When doing R&D on the Wave I started out on the conservative side and the boat was not significantly faster. Then I realized the mast was very stiff and like a telephone pole, so what the heck. I went mast head. Wow, what a difference.
And no signs of nearing the breakage point.

However, on thinner, bendier masts you are taking a chance.
On the H17, I would say to place the turning block about 33% above the hounds between the hounds and top of the mast.
You will get more out of the sail and still be pretty safe from breakage.
Good luck,
Rick