The 1/8" internal footings are the bee's knees for adding strength to the front of an arrow
You can get away with drilling about 3", and I have drilled up to 5", but by then you're in serious danger of drilling out the side of the shaft...which is extremely frustrating :D
Yesterday I shot a Douglas Fir arrow internally footed with 2.5" of tungsten without a point into a hard, solid block of wood and it survived one shot out of a bow that I was probably drawing 61#@28" (didn't want to hit full draw in case something bad happened)...it was going toward the target pretty crooked too
On the second shot the wood actually splintered around the back of the footing instead of snapping off. I was impressed.
Craig