So this is the minefield I have to navigate to and from my house, in a 13 ft tall RV.

Needless to say, I'm going to hit some trees here, so the mast was built to handle that.

Where the antennas attach it was built as two pieces which are held together by a spring.  

I started with the 6 lb draw spring shown, but at 45 mph it was starting to move around.  I changed it out for an 11 lb one and that seems to work well.

The two reducer flanges lay flat on each other to stabilize it when not being banged around, and a notch cut in the aluminum pole with a matching protrusion cut into the PVC pipe opposite it keeps it pointing in the right direction when it springs back.

The bolt that retains the flange on the AL pole also goes through the spring, and the other end is drawn up through the junction box by an eyelet.  That lets me adjust the tension from the top.

So now I can hit trees (slowly) and it just bounces back.  Yay.