Okay...the short story! Dad's 80 years old and has a bad shoulder. His injury has healed so that he actually can run a small saw just fine, but he can't pull the starter rope very hard without having a lot of pain. We were looking at my 018 and his MS170 and we noticed the 018 has that casting boss for a compression release. Wellllllll..........now Dad just thinks that would be the best thing since sliced bread if he had a compression release on his little saw. If I can figure this out...I'll put one in my 018 and trade him saws. He and I both know that there should be no reason to do this under normal circumstances.....but this is starting to attain a high level of "cool-factor" and so he really badly wants one! I may even put a 38mm aftermarket P/C in his 170. If I don't find a good pattern....I'll just put that AM cylinder on the mill/drill and give it my best guess. This is going to be fun!