Mike, the stabilizer restriction in MBR was changed.
3. BOWHUNTER RELEASE (MBR)
A compound, recurve, or longbow shot with no restriction on stabilizers or style of release. A sight shall have fixed pin, cross hair, or circle style pins without a lens or magnification. If circle style pins are used, all circles must be the same size. Sights may not be adjusted after entering the shooting course. Note rule change page 5, C-6, concerning peep sights. MBR archers will shoot from the green stake.
The above was copied from the ibo.net website.
Pete