These bolts are inherently in both shear and compressive loading, but it isn't the bolt that will fail in this application, it is the skin that has to resist the shear and lateral bearing forces. Hogging out holes large enough and filling them with something non compressive solves the compressive and much of the bearing area issue if the filled hole is large enough and very well bonded to the upper skin.
Putting a block in front of the clutch is just another way to provide bearing area from the clutch to the skin. The high density core material I used and the very heavy skin I have applied is probably more than adequate as is, but that would mean the lateral bearing area would still be primarily against the exterior skin around the bolts. In my mind the question is what is the simplest way to get a massive increase in lateral bearing area where it does the most good and that would be a small block glassed in front of the clutch. In the hogged out hole approach it would be necessary to also glass over the plug to completely bond it to the surface skin, otherwise you are relying on the size of the plug bearing against the skin and balsa. If the filled plug is pulled laterally hard enough it can crack away from the exterior skin. It probably would still hold, but you are back to a leaky situation.
I just think the steps at this point to add a small block is simpler and stronger than boring new large holes, filling them and then glassing back over them. In the case of the winches I will probably go the large bored holes and glass over route. I do think glassing back over the filled plug is important in these kinds of applications.
