Going to be doing much more stillwater angling this year, just wondering about fish finders:

1- Do you use one?
2- Is it beneficial to your success?
3- What brand/model do you currently use or have used that you would recommend, and why?
4- How do you mount the unit on your toon?
5- How much did you pay or would you pay for a toon mounted unit?

I have to watch funds, but feel like the addition of a fish finder could increase my odds of success. Henry's Lake is where I'll do most of my fishing and it runs around an average of 20-feet deep or so. Thanks for any help you can give me.