Thanks for your helpful, informative responses.
So it sounds like the 40 meter version may be significantly more stable than the 20 meter version because of the lower frequency crystal. In addition, the 40 meter crystal doesn't have to be pulled like the the 14.070 MHz crystal which eliminates another possible source of instability, correct? Does this mean the heating resistor is more optional for 40 meters?
Also, what is your source for the 7.074 MHz crystals?
Thanks again for your help and I'm glad to see we can order now!