I use a Mad Frog Transducer Deployment Arm (TDA) I bought at Mariner Sails for the transducer. No plate, just the arm. I use a RAM 1.5" ball mount for the head. Works well. The XDCR and TDA stay on the boat, the head goes in the truck and it's a quick install at the ramp. I like the TDA because it allows me to pull the XDCR up easily and keep it out of harms way. Plus it's a little further forward on the yak vs. the rear mount.
I knew that You are a gracious and compassionate God, slow to anger and abundant in lovingkindness, and one who relents concerning calamity.