I'm attaching the temp curves of a print with fan off (first print, left) and with fan always on after the first layer (second print, same item, right) -- sorry, can't post image links yet, to inline this.

Both of these prints use PID parameters derived by running auto-tune @190C with the fan running.  If the fan is off during PID tuning, I get a droop of more than 10C below setpoint and, on one occasion (when I let Slic3r turn turn on and off during print), nozzle dropped to 160 and stopped extruding (luckily I was around, so I cancelled in time), which freaked me out a bit!  But even tuning PID with fan on gives me a ~5C droop.  I guess I could up the gain, but before I do that:

Main question: do I run the risk of damaging my hotend (esp. after reading that temps higher up may be higher, and some ppl had the PEEK tube melt off?).  FWIW I seem to have a newer hotend (?), with a square heating block that appears to have a heat resistor inside it(?)

If not, then I'll investigate -- for now, I'm avoiding fan (even though it works wonders on certain prints).  I'll try modifying the shroud designs, because existing ones hit the heating block and melt -- right now running with minimal shrouding -- or perhaps try to devise a software fix. Any other ideas? Anybody else have similar issues? I couldn't find anything in the forum...

Thanks!