The front cheek plates are flat surfaces (angled in several directions) with compound miters. A lot of the geometry problems you’re running into are caused by the face in that area not being coplanar (flat). If you remove the cylinder shape and triangulate that face you’ll see that you end up with a concave shape.

If you run a boolean operation on a face with noncoplanar geometry the resulting n-gon will triangulate in a way that won’t shade well. Since the bevel tool is trying to follow the edges of these triangles you end up with something that doesn’t look good.

In the example image below you can see how I removed the the cylinder from the face, triangulated the face and ran the boolean operation again. While it’s not perfect it is closer to where it needs to be. To prevent errors like this it’s best to block out the larger shapes with compound angles / cuts and try to keep the resulting faces coplanar when you’re running booleans.

I had to manually merge down some of the verticies in the spikes that the bevel tool left behind. I’ve uploaded a blend file with the one side done and the other side ready for you to try beveling.

The settings I used for the bevel tool were a bevel amount of .1 and 3 segments. You’ll need to merge down the verticies highlighted in the image. T28_HullBevel.blend (494.8 KB)