speed vibration and comp tip

I have a ding in my mast about 10 inches past the mast tang. Can I retro a Comp Tip to the 1977 mast to take the wow out? I've noticed a friend's 16 has a comp tip which starts about 6 in past the mast tang...I've got the room- if this is a feasible fix. Secondly, When I get her up to speed, there is a vibration in the tiller that travels the whole boat. This is at high speeds and seems to be related to rudder alignment...ie rudders not pointing the same direction ever so slightly? How does one tune this? My old boat's tiller is riveted to the arms that connect to the blades hence I cannot adjust the relationship of the two blades...or can I?

These might help
http://www.hobiecat.com/community/viewtopic.php?t=1178


Sounds like you would qualify for a retrofit price.
http://www.hobiecat.com/community/viewtopic.php?t=78

As for the rudder hum, I seem to recall having read somewhere that you have to sand down high spots on the rudder. I just deal with it, because I'm too lazy to sand on my lexan rudders.

This article helps out with alignment. I spend a good hour doing this today. My 78 has a set screw on the side of the bar that will let me slide the end cap in and out to adjust my toe in.

http://www.hobiecat.com/community/viewtopic.php?t=467

Usually a vibration which you described isn't so much from the alignment of the blades as it is the trailing edge of the blades. One way to rule out the alignment theory is to kick up one rudder when you're up to speed, then change things around and do the same with the other. If you still have vibration with one blade up then obviously it's the one in the water (duh).
To eliminate the vibration (and sometimes the hummmmm) try tapering the trailing edge of your blades with a sanding block and some 220 grit sandpaper. Do this gradually, don't get gung ho and file a knife edge. Do a little bit then go test it..then do some more...and go test it, till you eliminate the vibration. I found taking the sandpaper between my thumb and index finger (like a taco shell) and squeeze the edge while sanding in up and down motions over the last 1/2 to 1 inch of the blade worked great.