Fishing rod butt clamp remix

Edit 13 June 2017: WARNING: I tried this out last week and found that the two uprights were totally NOT strong enough at the junction with the horizontal member to take the strain of the rod, or any bumping or disturbance. Will have to go back to the drawing board....

Mounting bracket sized for M6 nuts and bolts.

Taking inspiration from sirmakesalot's boat caddy:
http://www.thingiverse.com/thing:25502
and mistertech's excellent Ball and Socket Locking swivel components
http://www.thi