Do any of ya'll punch large mats of hydrilla that grow on lakes such as Kentucky Lake? I've seen people doing everything else, but never think I've seen anyone punching. I have the stuff to do it and Have thought on it just never done it.

I've never fished Kentucky Lake, but it would work.  Why wouldn't it? I'm sure more than one person is out there doing it. 

The worst that could happen is you not catching any and going back to your normal techniques. Worth a shot, doing something outside the box can really pay off.

My thing is I don't know what hydrilla looks like underneath. Once it tops out does it become thin or does it stay thick all the way down?

I live in California and some lakes I've fished are filled with it.  That stuff is pretty thick all the way down.  I've been surrounded by acres of it.  I've fished pockets formed on the surface and found fish schooled up in those areas.  Sometimes you can find underwater pockets created by the Hydrillia folding over forming something like a canopy and bass will school there too.  But it takes alot of blind probing around and patience to find underwater pockets.  

Punching will work on any body of water

It does not stay "thick" all the way to the bottom, the are tunnels, caverns, & voids.

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Not hydrilla (because it ain't here in NY..........yet) but I punch milfoil all the time. Sometimes it's the best thing going, sometimes it's not. Fish can be caught out of mats from the minute they form here, to the day they vanish late in the year. I find mat punching to be at it's peak in the immediate post spawn, the bigger fish use the protection of the mats to recoup, and usually bluegill bed colonies are not too far away from the edge of the best mats, so easy meals are around. And also mat punching shines, during high skies, the shade of a mat on an otherwise feature-less flat is a fish magnet. Mats are pretty easy to fish if you have the right gear IMHO, I have a two prong attack. Over the top with a frog, if that works I stay with it, or if they are just boiling or not coming up for the frog at all, I'll punch. If neither work, I am off to do something else.

Yes and it's very productive! As Catt said, it has tunnels, voids, holes etc... Go prepared for it with heavy gear. You will end up pulling a lot of salad in with the fish.

Everyday here.  65 pound braid and a 1.5 oz punch weight.  It's like a canopied forest.  Thick up top and open below.  The outside edges within about 5 feet are generally the most productive.

Pulling in salad in unavoidable when punching.  I like the RTR because at least your bait makes it into those voids below the mat before picking up grass and picks up less than most pulling it back out IMHO