Back in the old motorcycle days I would champher the edges or the hole
to give an edge for the epoxy to hold on to, and to remove a bit of weight.

Then I filled most of the hole with cork, and epoxyed both sides to hold the
cork. The weight that was added off-set the weight that was removed, and
it didn't change the balance of the crank.

It's called "stuffing the crank"....it increases the crankcase pressure.

FBD.