If you put some masking tape over the surface you are drilling it'll help with the splintering. Won't totally eliminate it, but it'll help some. Mash it down good with a flat tool.How do you like those holes when finished drilling into wood?
Are they fuzzy at the top?
Are they flat on the bottom so the case does not wobble?
Were the bits the correct size or are the holes a bit on the almost too large side?
I have not tried those bits but I have reshaped regular steel drill bits and reshaped paddle bits.
I have changed the nose profile to get a flat hole and not a cupped up hole.
I also reduce the cutting diameter to make a nice fit of the case.
I found pine boards fuzz out a lot and Oak is better as is redwood.
I must clean some holes with a sanding roll.
What wood are you using?
That is why I am asking so many questions