Here's my fix.
I used the same threaded end types on both ends...the mounting face for the motor looked flatter, so I thought I'd get a better bond. 
After I took the next picture I put a bead of epoxy puddy around where the motor mounts to the pcv end piece (only one screw is started in this photo. It snugged right up with both screws in (and I had to countersink).
Epoxy puddy anchors the thread coupler for the spike. Here it is before paint:
Painted:
Needs a bigger fur coat now as it is longer and wider than before. 1000% stronger too.
With this set up you can unthread the spike end and step it into the ground.
