Richard,

If there is a passenger air carrier that flies between Pittsburgh and some
airport near you, you may find that "as space available" air is the
cheapest.

Here's what I did to ship a seat from Phoenix to Milwaukee:

1) Weighed and measured the seat.  Not super exact.

1) Called the airlines that offered direct passenger service and got
   quotes for "as space available" shipping.

3) Wrapped the seat in one of those blue tarps and sealed down the
   edges with clear packing tape.  Of course, I labeled the to and
   from as well.

4) Took the seat in to the airline shipping terminal and referenced
   the phone quote.  Payment was due at that time.

5) The airline called the recipient for pickup when the seat
   arrived, in my case, 6 hours later.

I couldn't find any less expensive way to ship, $30 some in my case.  And,
I didn't have to deal with building a crate or carton.

Thanks,
Mike      '84 GL   '60 Vespa   '58 Isetta       --- Phoenix, AZ