I have had good luck with the slow cure (24 hour) Rod Bond U40 for both the reel seat, grip and butt caps. I rough up the contact surface of the butt cap and I also file a couple of small slight grooves with a very small triangle file in the reel seat under the butt cap to add a bit of bite for the epoxy. So far ithey have been holding up well with my 4, 5 and 6 wt rods.
Here's a thought.....I put them on with ferrule cement so I can take them off in the future if I need to. Of course, they may not make ferrule cement any more so that could be a problem. I recently pulled a cap off that had been there since '68, it seems like pretty good stuff to me. I use it for the reel seat too.