Maybe I'll just have to add them this winter for something to do

I don't think blowout occurs under 85 mph, I don't think you'll see much difference under 80 mph. You may have to run a slightly smaller prop.

At the speeds everyone is talking about in this thread, you should already have full external steering, but if not, DEFINITELY do not do a nose cone without it. The cone shifts the center of pressure forward on the drive, causing it to become closer to a "balanced" rudder, meaning less weathervane effect, and a potentially dramatic loss of stability if there is some slop in your steering.

just my $.02.

I completely agree,when my boat was 2 weeks old and still stock back in 2000 I put a nose cone on (that I didn't need) because boat only went 62 mph. As I modified the boat to go faster and it started to run mid 70's it had terrible chine walk.I first added imco twin ram external steering which helped but it still did it. I think the nose cone amplified it.Ive since ran it full to the helm and it runs straight as an arrow,even in the low 90's except when its trimmed to the max and running a big number and you start backing out of the throttle and boat starts to settle back off the pad you can feel a little twitch back and forth as v's start re-entering the water. I originally added the nose cone because it was a cheap mod and I didn't know any better. I agree,a boat doesn't need one until it gets close to running 80 mph,Smitty