[Elecraft] [K2] Crystal heater for better stability???

[Mike-WE0H]

Has anyone added a crystal heater to their K2? If I would add a heater 
to my K2, what oscillator would be the best one to do it to or should I 
heat both the 4mc & the 12.xx mc crystals? The radio is decent as is but 
I am used to zero drift when I work the Part 5 Experimental bands with 
my other radio's. I want to make my K2 very stable as it will be used on 
those bands.

Many thanks,
Mike
WE0H
K2 6698