If its like a lot of cues you can buy extension kits from prather. If you have a 3/8 x16 thread in the butt you might be able to use the Jacoby extension. I have a Jacoby extension that I use with multiple cues. I just bought extra bumper adapters from Jacoby
That's a tough one. I believe the older Predators just had a push in plug bumper. Even though you don't want to, it's easy eneogh to just get the hole threaded and be done with it to accept a quick release extension.
Why not just open the hole a little, glue in a phenolic plug and thread that M16x1.5 so it works with Predator extensions.
Want affect the cue in any way.
Since I like a light cue weight, I have taken the weight bolts out, and I can thereby screw the extension into the thread where the weight bolt used to be.