if you want a bombproof bond do the sanding etc but cut a groove in the insert and one in the mast so that once together they will be in the same position, when its epoxied the epoxy ring formed in the groove will keep the insert in even if no other bond happened.
In various application a metal expanding ring is used around an insert groove to expand in the receiver's groove locking the two, this works in the same way with the epoxy in lieu of the metal expanding ring.

Ps: that its a foolproof way to fix forever mortise and tenon joints, like the ones in chairs that come apart all the times, and that with normal carpenter's glue

BTW: why cant you glue the insert in and: drill, insert and rivet a pin, file the pin to the surface of the tube?