I have not seen anyone flying these with retracts.  If you don't like the fixed gear, just put the skid plates on it and hand toss it.  It flies like a dream, don't ruin that by adding a bunch of weight.  Plus you have to add a retract servo...yada yada yada.  When you start carving that wing out, it should be fairly obvious that you are removing structural material.  The wing must support up to 5 or 6 times the weight of the entire aircraft once airborne and you start putting it into high G maneuvers.
Good luck.