I've tried using a throat with a PTFE tube, but encountered the problem described in this question. It seems only a small amount of excess pressure in the extruder is enough to force out the inner tube. This makes me worry that with this particular part, I won't achieve a reliable configuration (and I'm experiencing some binding with the original plain steel throat, so a PTFE liner seems worth exploring).
I was wondering about the advisability of using a retainer to apply some pressure at the cold end - a nut with a washer soldered on maybe.
My goal is to prevent the teflon tube from rising up, so I can use this part and retain some resilience against excess extrusion pressure. I was assuming I had a slightly sub-standard throat part (in a pack of 6).
However, I now wonder if the problem was caused by too high a temperature (this is ABS filament) and maybe the teflon will be too soft to function as designed, so if I go back to PLA filament, maybe it is more likely to work without modification.