Oh yeah and this was the reply from S2S about their liners
"In regards to the reactor liners the 14 degree increase is a best case scenario. If you had a insufficient sleeping bag the extra heat generated would leak out.
The AP2 has a comfort level of -9 if you were in a situation where the temperature was closer to the lower limit of -15 you would be much warmer with a Reactor extreme liner than without.
If you had a sleeping bag with a rating of 5 in this situation even with a extreme liner you would not be warm enough."
Yeah technical answer there