The valve for a mechanical Ion - whether this kit or for a regular mechanical Ion - needs to be a normally open valve. The Fabco MSV-2 which is so popular for pneumag conversions is only available as normally closed, so it will not work properly. As far as I can tell, Fabco does not make a miniature normally open valve similar to the SMAV-3. I have a few designs for trigger valves that I'll be testing out soon, but as of now the only really popular options are modifying a cocker 4-way by plugging one of the output ports, or using an SMAV-3. Pneumadyne makes a few tiny 3-way valves that should work fine as well, but I'm not aware of many (if any) being used in any.