ajsr wrote:
why wouldn't you just post them and not worry aboutr it

the issue wont be that they are pressurised, it will be what the Xray up like.
and you will be relly happy when they pull you off the plane.
and yes you should be able to take them, a past friend on mine worked for Delphi suspesion designing suspension for the holden range, they flew him over to the us to pickup 4 (special) GM factory dampers spend 8 hours in the USA and fly home.
they were taken as cabin baggage for some unkown reason.
Perhaps because the cabin is pressurized and the hold isn't?
It's an interesting question, and in fact a decision I was forced to make myself - do I pack my struts in checked baggage - first question - what will be the effects of an unpressurized hold on a pressurized strut - second question - will TSA be calling me back to check in?
In the end I chickened out and tossed them in a box and sent them ocean freight.
Theoretically the struts should survive - I've seen race cars air frieghted from island to island.