Hey papajohn, do you run a pizza outfit? I live north of Edmonton and have about the same problem as you. We should both look to buy some land in San Antonio, Texas or something where it is warm in the winter...
John, get a whole bunch of plastic or wood paint stir sticks(they are about 14" long) and glue or glue gun different kinds objects at the end of each one. All kinds of coins(silver and copper), trash, pull tabs, alloys, iron, brass, lead, etc. and without glue gently tape gold rings on. Set up a stable test bench inside where it is nice and warm somewhere, situate the lower rod and coil so it is 90 degrees to the upper shaft with the VDI screen so you can wave the stir sticks in front of the coil while watching the screen at the same time. Experiment with all settings, take notes of the numbers, also listen for the different tones and sounds solid or broken up, and have fun. You will be ready for next spring with a running start.
I can use my X-Terra 70 inside(indoors) with no problem because of the digital V-Flex's immunity to most interference but my Musky picks up too much interference inside and chatters.