No I do use 4 bolts too..., just with that block, I designed it such that the bolts are not visible from the top......
as you can see from this earlier but similar specimen.
I'm using countersunk allen-key 8nc32 Stainless steel bolts.


This is what they look like
as for the closeness of the holes, indeed..... The closer together they are, without cutting into another, the closer to perfection each pin will be..