The "rear handguard retaining ring" should not affect the receiver bedding in any way: even when the receiver is in the forend and the front trigger guard screw is tight, the rear handguard retaining ring should still have some movement. If the ring is being trapped between receiver and forend, then you should adjust the channel where it fits.
On some rifles (especially when fitting brand new oversize wood, or if the forend is warped), you may need to create a small cut either side of the forend, so that the rear handguard retaining ring is free to sit a bit lower.
(Very hard to describe bedding issues in words only!)