Easier method
 

Why not make ONE accurate hole....and then dupicate it with the router table?

Heres how....

I use starboard
 

Grab a scrap....cut the undersized hole with the hole saw, then open it up to the correct diameter. It is only one hole....so not a bad task...

Make it tight!!!

Your panel still has the centers marked.....

Place the hole saw over the gauge placement, tape up your now perfect hole for the cutting template, then drop it into place.

Remove hole saw, open up the hole with a uni-bit,raise the cutting bit on the router and go!!

Hole cut, remove template and tape, drop gauge in hole!

Important, as you move to each successive hole....remove old tape and put on new...not worth risking the tape letting go...

In this case, I repeated the process 9 times. Took about 45 minutes total.

Now the Flo-Scan gauge.

First of all, I don't ever make my final cut into a finished panel. I always make a template just to be certain. Kinda follows the measure twice and cut once line of thinking. However, especially for this panel, I want to make the template because the flo-scan does not match.....so I can reuse the template to help create another piece for a trim ring or other idea I may require a same size hole for...

Seeing as there was no guide for me this time (like a hole saw) I simply measured the center of the proposed placement of the gauge and marked the outside of the template....

Notice the pen lines in the second picture....this helps me place it in the proper position after I tape it up...

So...I cut it all....except the Lowrance...

The next two images still show the packing tape as a protective barrier....but you can see that we have the same idea Mike approved into the final panel....but this is very far from finished in my opinion.

The next steps will be me adding the Lowrance....the template making process....transfer...final cut....then fitment.

While doing this, I will also start to get into the different possibilities of edge design, trim rings, relief cute...and aven illumination and edge lighting.....

As always....stay tuned...

Lookin good rich. And I'm learning.