Now is when you have to check the accuracy of the hinge slots. Most of the time the centering of the rudder to the fin will not be correct. Now is the time to check that and adjust the hinge slots with the saw blade to move the rudder sideways until it is centered. First pic shows the rudder off center. Then the remaining show a correctly set rudder. Sorry for the somewhat poor pic quality.
I like to use the hysol for gluing the hinges in to the fin. It is an excellent bond plus it gives me plenty of time to get things positioned correctly. I use a short nozzle tip and insert glue in to the hinge slots, then some on to the hinge. On the hinge just make sure glue is in the holes of the hinge and then just some on each side. Only put some on the tip of the hinge. You don't want too much clogging things up. I insert all of the hinges about 1/2 way, then using Q-tips I clean off the excess glue. I then slide the rudder all the way on to the fin. Again using q-tips I clean off any excess glue, then tape the rudder in place, making sure it is centered on the fin. Now you let it set overnight and once cured it will be cracked loose and you'll be good to go.