I have a Bass Tracker that I want to mount some rod holders to along the gunnel. They will probably be Driftking or Monster holders. The bases will have to be screwed down as there is no access to do bolts. Do you recommend the 2 screw or 4 screw base? This will be for catfishing, anchored and drifting.

The more the merrier.

Personally I prefer Folbe rod holders. Don't see them much down here but I've got six bases mounted on my boat.

I used the Driftmaster 2 hole bases. If you use a reel with a clicker, you aren't going to have to worry about a big fish pulling it off anyway. I drilled and tapped my gunnel, but I don'r remember if I used #8 or #10 screws to fasten it down

Food for thought. Riv-nuts are also an option if you have enough void inside the gunnel. The pull-out strength of a riv-nut is much higher than a machine screw would be in something like 1/8"-3/16" aluminum. You could even go w/o bases all together and screw the rod holder directly into an installed 3/8-16 riv-nut. The more you pull on a riv-nut, the tighter it gets, until it pulls out, of course. But if you rip a riv-nut out, you were likely going to lose that rod and holder anyway you had it mounted.

http://www.amazon.com/20Pcs-Steel-Rivnut...keywords=rivnut

I had considered Riv-Nuts to attach the bases, hadn't considered using one as a base. I'll have to check how much room I have in the void. That certainly would be a clean install.

Rivnuts are going to have a lip at the top that will keep a flat base such as Driftmaster and some of the others from sitting flush on the gunwale.
I don't think they are going to get a lot of stress on them to the point of breaking off. If you are really worried bout that, I would enlarge the holes in the base to accept a #10 machine screw, drill and tap, and mount the bases with those.

The gunwale on my boat is not flat, it has a slight radius to it. That was the reason for my initial question. A 4 screw base will not sit flush on both sides, it will require washers on one side. I was not sure if a 2 screw mount would hold up to a large fish or repeated use.

If I were going to do it and wanted a professional looking job, I would take a piece of Starboard the size of the rod holder base, lay a piece of sandpaper on the gunwale rough side up and use that to create a pad to mount the base on. You could do the same with a 4 hole mount if the gunwale is wide enough. Look at your bass tracker again. You may be able to drill copletely through the gunwale and use lock nuts on the bottom, cutting off the excess screw material. It's usually pretty easy to figure out how to attach stuff to a tin boat. I had to get pretty creative on mounting deck cleats to the gunwales of my Seaark, but it can usually be done with a little thought.

http://www.ptreeusa.com/ttrackproducts.htm

This is what I used on my Bas Tracker. Mounted it to the inside of the gunwale and used monster rod holders with the track mounts