Mauser, I also have replaced my T/C Hawken Frizzens with Lymans and have been doing this for years. I wouldn't worry about it being "loose" once it is open. You only need enough resistance for the flint to throw sufficient spark into the pan. Try turning out the lights when you test fire it (unloaded of course). All you should have needed to do with this frizzen is to file down the sides that fit into the mating groove of the lock and replace the screw. If it isn't opening, place a very tiny amount of anti-sieze on the spring and work the frizzen open and closed. I also position my flint to where it is just about touching the frizzen at 1/2 cock and no more than 1/16" gap.