I have been following this discussion but I am still not certain what is the final (if any) conclusion about gluing the PEI to the MIC-6. The Pliobond contact cement #25 sounds like the best choice. The 3M 468, by contrast, is rated only to 100 degrees Fahrenheit, so I can't imagine why people are using it for something that is normally heated to a temperature well above that.
I've used Plibond #35 to adhere my silicone heater to aluminum heat spreader on my giant delta, and then also to adhere cork insulation to the back of the silicone heater (creating a sandwich). It takes a good 2 weeks to fully set and it stays somewhat rubbery after. I would not use it for PEI application. 468 tape is very effective for adhering PEI to boro, never tried it with aluminum directly. The issue with Plibond is it is hard to apply the cement in an even streak free fashion, #25 would be even harder, then you get imperfections under the PEI, which you don't want as PEI is thin, and the adhesive needs to be flat and bubble free.
Not sure where you found the rating: http://multimedia.3m.com/mws/media/1040 ... -200mp.pdf
says these tapes are rated up to 400F, and can withstand hours at 130C+ Note the rating is for highest bond level, so bonding may soften at 100C, but not enough to pull up to have issues with ABS warping etc.