New Information:
First FWC says that tin canning almost always is associated FWC that have had a snow load. Take that at their word. I guessed that the top sheet on my '16 Hawk is about 88 sq/ft.....using the table in this article [scroll down for chart] you can see that any appreciable snow of a variety of types [water content/density over time] can quickly exceed the FWC statement that "the top can take 1,000 lbs of snow". Hypothesis, WAG, is that too much snow either bowed the top sheet and or top frame and stretched the aluminum top sheet creating bowing in areas between roof framing.
https://roofonline.com/weights-measures/weight-of-snow/
Recent Observations and Clue For A Fix:
The top of my Hawk has 6 length wise aluminum frame members [look location of these above the inside liner wooden strips]. The obvious areas of bowing/flex from distorted top sheet on my top was
between these frame members. A lot of convex bowing of top sheet between those frame members. Bracing laterally across these frame members did not stop the tin canning, but putting weight [used 2"x 4"x 3ft for area and weight test] l
ongitudinally and centered between these 6 roof frame members did dampen or eliminate the movement up and down of the top sheet in those spaces and tin canning.
My 2 solar panels [on Yakima Rails] cover about 30 sq/ft of the top sheet and while top sheet does flex more in uncovered areas of top sheet the 'why' tin canning can occur under the solar panels is a puzzle. Perhaps the weight on Rails caused top sheet distortion.
I have been skiing with the Hawk and have had up to 12" of fresh [powder, low water content] overnight on top sheet before I scraped the top off with a rubber snow remover rake. Never did the snow sit long on the top and most of the other times I had a maximum of 6" snow for brief periods on top sheet. Never ice or "Sierra Cement".
So, all this and $3 with get you a cup of crappy coffee....My next move will be to purchase aluminum flat bar and using 100mph tape place sections of the bar between the longitudinal frame members of the top sheet while seeing if I can replicate wind produced tin canning with my hand.
Phil
Weight of my two Zamp panels [160 & 170w] and mounting frames about 55lbs; no idea of weight of rails or two power roof vents.