What ever you use - be sure to secure the rod/reel with a short safety line. A big fish on trolling gear can really put some leverage on a homemade holder.
I found out the hard way - by blind luck the rod did not go overboard.
Be careful with the white PVC - sunlight will weaken it after time. If you know an electrican - you might be able to get short pieces of 1 1/2 or 2 inch conduit. It will rust slightly where cut but if it's free - you got a good deal. Drill a hole through the bottom for a bolt and you have a pin to lock the gimbal in.
What could be more mundane than dying of old age or of natural causes when there is death by misadventure to be pursued ? Skip