EG ULTRA CLASSIC, you are correct in the assumption that the small amount of aluminum from the drilled out part is expected to blow out the exhaust. If not, it's all under warranty, they can re-lick that calf and do it right the next time. The actual hole cut in the head with the drill used is less than 1/8", quite small, and every thing is done in stages to where the final cut actually cuts thru a very small amount of metal. Sounds like it will work, and I guess it does, they've done it many times before. 2.5 hrs labor plus gaskets for the rocker covers. I have a set of HD compression releases already if I decide to do this. The JIMS tool used to do the heads cost more than what the HD shop will do the job for. If I bought the tool and did it myself, I'd end up loaning it to everyone else at my expense!!!! so I just well let them do it! PACO