Here's how I did it on my PA. (technically It's how I did it on both my Revos and my Outback too) I realize there are other ways to do it, but it works for me. Also if your more of a clean out of the box guy RAM mounts makes a sail mount holder.
A little 1/2 inch PVC and a 45 degree elbow.
There is a hole drilled through the poly cutting board material I use for the base. The connection is made by using a slip to thread coupler and a threaded piece of PVC to attach the cutting board to the pipe.
The mount for the FF is mounted tothe poly cutting board with SS bolts and SS nylock bolts. (I got mine from Capt. Dick)
Using your favorite tape (duct, friction, electrical) and give it a couple wraps to snug it up. I used black electrical tape and have only stripped it off and reapplied once in two years. I also added the holes for the bungee, (it held that thing on in a nasty roll in the surf)
Here's the power. It's a cheap large acrylic dry box from wally world. It has a female trolling motor connector (they were on the discount rack at wally world and I bought a bunch at a dollar a piece) It just holds a twelve volt 9.0 amp per hour battery perfectly. (I also have some AA battery blocks that have matching pig tales so that I can use them in the box if I'm away and cant recharge the big battery)
Closed up Water Tight
Transducer gooped behind the sail mast. (by the way the sail mast screws out for easy placement. righty tighty, lefty loosey).
The ducer connections! I used the male trolling motor attachment!
The battery Velcro'ed in place and the wires connected.
Cooler liner back in place. Yes, Virginia you can have a Fishfinder and fermented adult beverage storage!
Buttoned up to hit the water.
Now maybe I'll get off my butt and paint the PVC black (I like to use black spray tool dip)