Jake, Very cool! It is similar to what I have done, except I never thought about a spring loaded head. I mounted my transducer on a shaft just like yours and attached it to a cross member just below the front of my seat. I left the hose clamps slightly loose on my frame so I can swing the entire shaft and puck out of the water, very useful when I'm going to bury myself in the weeds.
Mitch

-edit-
Hope you don't mind, I hijacked the pics and added them to the rigging gallery, very good stuff.