.......yeah..
You have got to be very careful not to block the internal port that works your bellows.
I've been known to use a thin piece of chart paper, then cut it out. You can also go to the auto parts store and probably buy gasket material, 1/16" or 1/32" and cut it out yourself.
But, if you use gasket maker. Really spread it thin and be careful of the internal port!......:cheers: