ok i i am added some triangle stock to my stableizer and fin to make sure it is solid what is the best way to removed some of the monokote off of the balsa so that i can epoxy the triangle stock to the stableizer and fin.
thanks in advance

Use a NEW #11 blade to very carefully cut the covering where you want the triangle stock to go.
Put just enough pressure on the blade to only cut the covering, you don't want to cut or score the wood which could cause the fin or stab to fail in flight.

Another way is to use a soldering iron with a pointy tip. Draw the outline that you want to cut out and "cut" on the line with the hot iron. Move quickly and evenly and the iron will leave a smooth cut with sealed edges. Don't stop the movement with the iron still on the wood or it will scorch it. Just keep it moving steady.

Jesse

Also, when you glue in the triangle stock, taper the ends so that it's faired into the fuselage and stab, cover the outside edge first, then glue it in. It's a lot easier than trying to apply covering once it's in place.