Mix up epoxy and glue the grips in place. Be sure to put the screws back in and lightly clamp the bolt hole area til the epoxy cures. Wipe off the excess epoxy before it cures.
If that is the modification you are talking about, you have to do it before you use the blades on the heli. Wooden blades are very dangerous if you don't glue the grips to the blades.