Firestone John Wood Liquid out

I have a firestone john wood, I believe, 10 gallon keg which I just replaced the gas and liquid posts on. The plastic insert however is not sitting tightly against the dip tube. Is anyone familiar with these at all? The plastic insert almost seems too big, but I haven't seen any variation in sizes of inserts anywhere. Is there supposed to be a spacer that sits under the dip tube flange to raise it up a little?

Thanks

Feel kinda dumb. I flipped the insert over and it tightened up and seated good. But I bought it with the plastic insert "inserted" the other way. Anyone ever run into that?

At least you used an adverb in your original post (tightly)! I haven't done that, but I've had much, MUCH worse beer accidents than that. The most recent was that I didn't notice a split o-ring on a corny keg and came home to three gallons of IPA in the bottom of the keezer.