The slit silicone tube is pointless; the top can't slip off, only go bit off-center, and in a matter of a half-dozen roasts the roastium build-up on the glass top will keep it from slipping too.
I like the silicone tube a lot. It softens the contacts. Yup....it comes off and has to be put back on. It's worth it. Peter has this one wrong.
Why is 'softens the contacts' important? Are you concerned about breaking the glass? That's silly.
Spending money on the silicone, spending time installing it, spending time putting it back on, all when it's unneeded... that's worth it? If you're going to add cost/complexity to any project it has to have added some value to the project. If you simply like the silicone tube, I would not fault you for using it. My post was directed at someone giving advice to a person new to roasting and trying to keep him from thinking the added cost/complexity of the silicone tube had any real benefit, which it does not.
I may concede part of the discussion, IF a person is using the UFO for the bottom, as they're smaller in diameter to the Stir Crazy.