Hangar Flying

This is sort of a weird question and I'm asking to see if real world is what
my theory tells me is right.

What I would like to know is basically what if any changes were noticed
when you changed from or to a prop hub extension. Anything is helpful
here so if all you noticed was more exhaust on the blades or quieter or
faster and so on thats what I'd like to know.

I am curious if there is a optimal separation distance from the trailing edge
of the cowling to the prop. If it doesn't seem to matter then I'm fine,
if it needs an extension then I need to replace my crank as I have
the thin flanged lycosaur crank which is unfriendly towards these.

And now for something completely different. Almost.

I'm also wondering if anyone has tried to modify the exhaust  so that it
exits outside of the prop arc. I know that would take a bit of doing but
I'd be willing to bet someone somewhere has done it.  Again wondering
if the improvements were that measurable.

I now return you to your regularly scheduled reality....

Dave