I'm not overly familiar with the 120 though I know it has a convection fan. Does it have one or two fire pots?
The convected air may offset the direct down to upward flow of heat, in which case may alliviate the dryness issue.
Which way are you smoking briskets now? If you're happy with the results and scoring well, leave well enough alone. You can always practice both methods in the off-season and see what works best for you.
If I owned a Jambo offset, I'd probably go with fat side up till plateau and then flip. Lacking $12K and a Jambo, I'll stick with fat side down in my 100