Many "side-cut" electric can openers leave nice, sharp edges without distorting the cylinder. One can "make" a hole saw (for use by hand or with a drill or drill press) from small-enough juice cans for 2-inch eyepieces.
I've also read about soaking open-cell foam (water), squeezing out much or most of the water, then freezing it - yielding a fairly rigid block which is better able to "handle" hole saws, Forstner bits, and/or even spade bits. (Using spade bits to drill into dry foam is NOT a good idea! )
- BUT... I just ran across this method, which looks promising...
Best wishes and luck.