Look at the pictures please this is the only way I can make it secure because I do not have a downstem right now I think it is fine bcz no smoke will touch it?
You should look up Teflon flu...and remember...this is talking about fumes inhaled from within a room containing heated Teflon, not directly inhaling it out of a bong where the concentrations would be much, much higher... TL/DR...bad idea...
Personally, I'd just use something else until you can get the proper piece to make it work as it should...
Okay I took part of the broken downstem half of the part where the bowl goes in and am using that as a shim to keep the bowl decently flush so that should be fine only glass no tape or anything?
Should be okay...glass is relatively inert at things other than super high temperatures...best to avoid tapes or things that can off gas unknown chemicals...