Try the Raptor handle just as it comes out of the package as it may drop in and work that way.
If not you will probably need to do at least steps 1 & 2 of the following.
1) File down the raised area on the front top so it is flush with the top of the handle.
2) Then from the front, through the hole, use a round file to remove the raised area of the channel so it is flush with the rear portion of the channel.
3)If the handle still does not fit properly you need to deepen the full length of the channel. Mine only needed .010" removed, but others have had to remove as much as .030", which would have made mine awfully thin. this is probably best done with a milling machine and a ball end mill. With lots of patience it can be done with a dremel.
Be sure to try the handle between each of the three modifications.