Here is a way to install hinge type plastic hinges such as Dubro or Klett and make sure they are perfectly straight and centered.  It takes a little more time but even with the electric slotter I am a spastic. So for all you die hard plastic hinge folks who happen to be spastics like me, you might want to try this if you are building from plans.  This shows how to do it for the stab and elevator but on certain types of wings you could do this on the flaps too.

1.   Cut 2 pieces for your stab and 2 pieces for your elevator that are mirror images of each other from the thickness required.  In this pictorial example I used some scraps of 3/32   The one constant will be the 1/32 balsa that will be the meat of the sandwich..  
2.    Using the cut out and shaped pieces of the stab and elevator, lay them over a piece of 1/32nd balsa and trace and cut out the 1/32nd so you have a mirror image of the stab and elevator.
3.   Take the 2 pieces of 1/32nd and butt together the trailing edge of the stab and the leading edge of the elevator and pin them to keep them from moving around.
4.   Lay your hinges with the barrel in the hinge line and trace the outline of the hinge.
Space the number of hinges you will be using evenly along the hinge line.
5.   Carefully cut out along you outline for the hinges.  Remember this is 1/32nd balsa
And you can split it easily.
6.   Lay the 1/32nd piece that is cut out for the hinges on one piece of the stab and the other piece of 1/32nd on the piece that is the elevator.  Makes sure you have the slots matched correctly.  You now have the bottom piece of the bread with the meat lying on top of it.
7.   At this point you can glue the 1/32nd piece to one half of the stab and the other piece to one half of the elevator.
8.   Lay the top pieces of the stab and elevator on top of the glued down 1/32nd piece and glue them down.  This is the top piece of bread if you will.

You now have a perfect and centered slot for the hinge to fit into.  You can glue the hinges in the slots two ways.  You can lay the leaf of the hinge in the pocket and glue it in before you glue on the top piece or you can complete everything and using a sliver of a playing card, apply epoxy in the slot and then stick the hinge in.  That part is up to you.

You will notice in the pictures I show the hinges connecting the stab and elevator without a recess notch for the barrel of the hinge and one picture that does show where I notched out for the barrel.  Again some people do this and some do not.

Hope this makes sense.

Mike

Good point Ty.  Thanks for that.

Mike