I was probably the guy that posted 5.5 feet in front of the boat, as I don't think anyone else would put it that long. If all you have are nice, relatively steep concrete ramps, 3 feet or so should be fine. I prefer the longer tongue because it gives me more room between the truck and the trailer, so tailgates don't hit, and you aren't constantly backing into the boat when pulling stuff out of the truck. Also, on shallow ramps, it does allow me to launch/load better, although there aren't many shallow ramps where I fish. This morning, however, I launched right after a guy with a 16 foot Carolina skiff, with virtually no tongue. This particular ramp is somewhat shallow, and he had to back in until his front wheels were wet, putting his back axle/differential/brakes etc under water. Even then, he had to power off. I backed in, and my bumper was even with the water, giving me another 2.5 feet before the tires got wet, and my boat was completely floating, held on only by the winch strap. I personally wouldn't have a shorter tongue unless I absolutely had to.
I personally don't like the slicks, but that is just because of the way I launch and load. If I have a second person, I will unhook the winch strap, have him in the boat, and back in until the boat floats off. When I load, sometimes I will power on, and the driver will pull out immediately, without wasting time to hook up the strap. Couldn't do either if you had the slicks. Now, if you do feel you need slicks, the Walmart cutting boards are the way to go. I had them on a previous boat, and if I ever have a boat that I needed to have something other than carpet, I would definitely go with those again.