I hate to try a new monovalve because the only ones now available are MTC aftermarkets, and I and many others have had a bad experience with.
Quick FYI: Our engineers are currently redesigning our Monovalve Repair Kit 0008350644R, and the improved version should be available in six to nine months. The primary change is adjusting the rubber diaphragm profile a bit for easier movement, and some minor changes to the smaller pieces.