Best fish finder mount for non lowrance ready kayaks

[Kevin]

Been off a kayak for the last 10 years and came across a great deal on a OK prowler. I've already made a bait tank and tested it out in DP yesterday. Now I need to add a fish finder. I have to say, fish finders have changed a lot in the last 10 years. Back then building a moat and filling it with two part plastic epoxy was a pretty good method. Now there's so much more tech with the transducers?

So what is the best method?

1. Duct seal? will this work with down scan imagining?

2. Over the side mount? Ram or scotty? is this method a PITA? or not too bad?

3. What about rigging something off the rudder mount hole? Bad idea?

And is down imaging, side imagine really worth it? would it be better to just pick up an inexpensive Garmin Striker 4 with GPS, duct seal it in and be done with it?