per their website:
"...so as to eliminate balance and material integrity problems" balance shouldn't be that big of a problem but material integrity is a big issue to me. even in disk brake applications, holes that are post machined into the rotor are known to lead to cracking after prolonged use. the consensus among people that want a performance improvement is that cross drilling is for race only, no benefit on the street, and slotting is ok. this is not a perfect analogy i know.
the issue is fatigue cracking after many many cycles as you'd find on street driven cars. race, you put new rotors on before heat cycling becomes an issue.
the holes will accelerate wear of the brake shoe too, think cheese grater.
also, that website isn't an article as much as an advertisement...
www.chtopping.com referring you to C.H. Topping and Company to perform a service.
i googled it a little, seems to be pretty common practice actually, i'd just be leery with drums that are hard to find, or parts that have been turned and are near the thickness limit.
