One thing to remember, this light is supposed to be 3 meters higher than your bow light, I think.
What I did (which is very redneck but works perfect) is mounted a piece of pvc (maybe 1 1/2"x12" long???) on the inside of my transom at a slight angle. Then I bought this https://www.academy.com/webapp/wcs/stores/servlet/Product_10151_10051_12673_-1?N=581131708 and secured it to the end of a wooden closet rod with electrical tape.
All I have to do is slide it in the pvc and connect to battery. When not in use the pvc doubles as a rod holder.
The closet rod started putting a small dent in the bottom of my boat so I took a 3" piece of pool noodle and made the hole on one side big enough for the closet rod to fit in to act as a cushion. Just make sure when you install the pvc, you leave enough room under it for the pool noodle cushion.
I don't have any pictures of this and I hope I explained it clearly. I will try and get a few pics this weekend while I'm at the camp.