FWIW, IIRC seems walnut have been the most prone to cracking. Do love my Cherry wood and it is on pretty much all the time. Often I forget to turn it down and it will stay at 6.5 for a day or two. No issues at all.
On the silicone.... It has been included on GonG adapters for at least a year - not quite as long on stems IIRC. Some users didn't like it and removed. Could be yours is an older one or that previous owner just pulled it off. I've added it to my older GonGs. Think what I used was 3/8" ID, but not positive. Have pieces of a few different sizes all in same box.
Primary purpose is to keep from burning fingers. Works well for that. Also is nice to use if you like to pull the GonG when you clear your piece. What I do is roll it about 1/3 of the way down on itself to create a ledge. This makes it very easy to snag the GonG with your pinky or ring finger (or both) when lifting to clear. You'll be surprised how much difference the little ridge makes. Just set it up like this -
BTW.... think this is at least the third time I've posted the tip and this pic. Use the search function! It is truly your best friend on FC. Upper right corner of every page. Just check the appropriate box if you only want to search a specific thread. My original post also has some more good info - much on screens and adjustment for great hits. Check it out
here . Took me all of about 2 minutes to find it with the search function.