Yes... A tremendous about of paperwork, expensive certified engineering,
flight testing, and of course insurance. Once you're done with all that,
you have
*one* engine/airframe combination that's applicable. Put the same engine
in a
different airframe, and you have to do it all over again. (Well, maybe
not all of it,
but a lot of it).

Hmmm...
Paperwork is free (except for the time to manage it).

What type of certified engineering is needed?
Just like you, I am an electrical engineer with all kinds of certifications
(P.E., etc).
I also know plenty of mechanical engineers with their own certifications.
How expensive is it? Do you have any numbers? I'd be interested in
knowing.

I'd be more than happy to flight test a turbo in my plane!
Experimental planes need 40 hours. If the requirement for an STC is the
same, I would gladly do that standing on my head!

I agree that insurance is probably a bear. Any ideas on cost or where that
information could be found?

I'm sure a lot of people smarter and more enterprising than me have already
investigated this as a possible business, but I'd still like to see the
numbers to see if it is feasible. It seems to me that if you started with
an STC for a couple of the more popular models, it might be possible.
But then again, I'd need to see some real numbers.

And, of course, the whole reason I'm interested in this as a business is
because I really want to turbo-normalize my plane ;-)

Thanks,

Adam