Being from the "old school; I still use the Sig flat hinges for all my builds. This is so I can cover the hinge line on both mating surfaces with a strip of Monokote prior to covering the entire airframe. I measure the centerline and mark it on both surfaces, say the rudder and fin. Using a #11 blade I cut the slit where required for each hinge. Taking a strip of appropriate size Monokote I apply to the control surface mating edges. Then I cut the corners off each hinge, about 1/8", to facilitate hinge insertion and mark the centerline of each hinge across the short dimension. Insert hinges up to the marked center line on, say, the rudder. Mark two location points centered on the wood over each hinge location and drill completely through the wood and through the hinge with a 1/16" drill. Take round toothpicks and cut each in half; insert each half through the wood and hinge and push down the toothpick until about 1/8 " sticks up. Take a TOENAIL clipper (it makes a clean and straight cut) and carefully cut off the toothpick flush to the wood on both sides of the hinge. I usually use a small hemostat to grab hold of the extra length of the toothpick to keep it from flying around the shop or into my face..BE careful! Now, doing one side of the control surface at a time and one hinge at a time you add a drop or two of thin CA to each toothpick spot and go over the area with some fine sandpaper. The sanding will usually fill any small imperfections and make the area smooth. Flip the control surface over and do the same on the other side.

Now, take the completed rudder that you have toothpicked the hinges into and insert that into the fin which you have previously slotted for hinges, Monokoted the hinge line (which is what I use), and re-slit the hinge locations in the Monokote. I use a metal 6" shop scale placed between the mating rudder and fin for spacing. Push the rudder up to position against the metal scale and mark the two toothpick locations, drill as above, insert the toothpick halves to hold everything in place and finsish off as above. Repeat for all hinges. When finished you will have a very nice, small gap, mating between the control surfaces that will not only look great when you finish covering the model, the hinges will stay where they belong.

In truth it takes longer to describe the process than to actually do it. If you like to use the flat hinges give this method a try for a neat way to install these hinges. Hope this helps.

Soft landings.