Bell 412, 407 tailboom to fuselage attachment question

[Rotorcraft-Design]

Good evening, 

I have seen how the Bell heliclopters 412, 407 tailbooms are attached to the rear fuselage with 4 bolts penetrating the closing frames via holes. Bolts are aligned with aircraft longitudinal axis. Basically these 4 bolts are taking tension and shear loads. I wonder if those holes are clearance holes (larger diameter than the bolt, or they are close tolerance holes. Normally when we design interfaces of these kind, we try to do clearance holes allowing some play to account for the tolerance variation in position and size. But for an helicopter that is subject to cyclic loading (vibrations) how this joint stay tight avoiding any fretting or risk of loosening. . 

Thank you