Mine was a tight squeeze, but went in fairly easily with a little twist, try kind of screwing it in, but don't force it too hard.
As an alternative you can purchase some food grade tubing, I believe 1/4" fits.
I love my LB, but the screen has gotten dirty. It's stained reddish brown and has a few dark spots at bottom of trench due to combustion I think, also there are some dark spots which are most likely from the amber glass I tried to vape.
It seems crazy to me that MF says there is no need to...
Got my LB a little over a week ago and am loving it. Still learning how to best use it, combusted the trench for the first time last night so I am still adjusting.