I soldered the vent tube in all my gassers.
Some of the local flyers here place a piece of sponge (like you get in a servo box or airflter element)
directly over the diaphram cover. They glue a circle of foam the same size as the cover and about 3/8" thick.
This might work for you if you don't want to get into soldering, be careful not to block the vent hole!
I have never tried it but it seems to work.