Don't forget that there is an area to take into account here. If you have a very thin sheet, bearing area can become significantly less than shear out area, and the sheet fails in bearing.
gyro,
If it is possible at this time to modify the mould, or if a new mould is to be produced, why not mould the countersinks as part of the panel? You may also need to consider laying extra plies along the fastener line anyway to ensure you have adequate bearing strength in the cover to take...
Best advice is, try to change the design. If bolts are shear-carrying, the danger is that the shear load tips them instead of shearing, so after repeated load application there is local bearing failure in the outer leaves of the joint, and the under-head radius of the bolt is subject to prying...
