SMA connectors are quite common for high speed interconnect in applications like this and you would think there would be plenty of app notes or examples to copy, but I was surprised how difficult it was to find a suitable reference to copy.  I did find some information online to point me in the right direction.  One issue I wanted to address was the fact that the pad for the signal pin is significantly wider than the trace width for a 50 Ohm trace.  This article by Dr.  Howard Johnson describes some techniques to deal with this ( http://www.sigcon.com/Pubs/edn/TaperedTransitions.htm ) I'm not going to go full tapered, but I did round the pad and cut away a little off the plane below to reduce the effect of the transition.