I have a Craftsman Dremel look-alike tool, but I don't have a router. Given that I only have foam to route, I made this little fixture to do just that with it. Depth adjustments are a little coarse, but it works fine for foam that will have fiberglass applied over it. Further, it's nice and light so it doesn't dig into the foam as you slide the jig around and route. I used this to route the flight control depressions.

I cut this simple circular jig on my bandsaw and used it to route, using my poor man's miniature router as shown above, the flight control depressions. It cut a real nice, even depth, depression which I then sanded perfectly smooth. It turned out pretty nice. If I have any other small depressions or cutouts to make I'll do this again.

This is the 3/8" foam used for the fuselage sides before it gets glued to the jigs for later steps. I thought I'd get crafty for my fuel sight gauges and route a simple square and set them in. Well, it turns out you should really mount them later so this was a bad idea.

In this picture you can see how nice they went in the recesses I routed. Like I said, though, they really should not be mounted until you are completely done with the fuselage interior to avoid damaging them. Someone might be able to work out a way to mount them ahead of time, but, unless I was building my second or third Cozy I wasn't confident I wouldn't screw something up so I waited. I had then, of course, to fix this cutout. My fix did improve the situation, though, read on.

Ok, my first idea didn't work so I cutout the foam altogether to start over. This foam will get fiberglass on both sides so I don't think this is too critical. I cut the area slightly bigger than the fuel sight gauge so I could make some beveled pieces of foam, glue them in, then still have 1/2" on all sides of the gauge in case it needed to move slightly and would have plenty of room for a good flush mount.

I again used my band saw, this time starting with a 3/8" piece of foam cut to the right width, to make a beveled piece to "angle the gauges forward" as the directions recommend. This piece filled the back 80% of the hole (shown in the picture above) then a smaller piece, at a larger angle, filled the front 20% of the hole. This gave the fuel sight gauge a nice flat place to mount but also angled it forward nicely. If you are interested, see the AutoCAD drawings link from the main menu on the left.

Here's a close up of the fuel sight gauge sitting in the depression after the depression parts were epoxied into place. Left on the picture is forward in the airplane. You can see I had to sand the foam on the top and bottom to get it to blend in with the pieces I cut as indicated above. This is about all the angle you can get on these without making a bump on the back side. 

Once I had the fuselage sides contours complete, I test fitted the fuel sight gauges from Vance Atkinson to make sure the depressions I made for them were in the right place.