XTP HP cavity crushing during seating

[DenStinett]

Are you using a Round Nose Seater Plug or the flat one for Trun Cone Bullets ?
The Round Nose plug will scrunch your Hollow Cavity

That's also a good thought. I just pulled the plug out of my Lee die and sure enough it is rounded (hemisphere).
Unfortunately it isn't reversible.

Are the other plugs completely flat?

RCBS has both flat and round in there standard Three Die Carbide Set
They also offer some specialized i.e. Gold Dot Plugs
But when it comes to the High End HP Bullets, you gotta use that Flat Plug
The Round Plug will close-up that Hollow Cavity