Never surrender, never give up, never stop building!
Ok, so maybe I spend a litle too much time in this hobby
Have you decided which plane to build yet? Or, are you first thinking of building a test mule to evaluate your contra rotating motor system?
Other neat possibilities:
Martin Baker M.B.5
Boeing model 400 (F8B)
Douglas A2D Skyshark
Fisher P-75 Eagle
If really ambitious, there are also multi contra rotators, Convair R3Y Tradewind.