The downside of removing too much material from the slider is that it obviously thins the tube.
For a big ding, Musky's way is worth a try. A plug to fit the tube, tapered at both ends and with a nice piece of threaded bar to enable it to be pulled out, hammered in with a little bit of red heat should do it. Taper on the topside gives a second bite on the way out. Not too much heat, or they will stick. Not ideal, but worth a go in the absence of any prospect of coming across a better part in the short term.
Add..Musky's disclaimer.
Swarfy.