OK. You've got little problem here. That's a very low, very slightly sloped but light weight cone drawn there.
If you took an apparently very conservative approach and assumed it was a simple round tank of equal height and equal outside diameter, your wind load - sideways! - would be more than what would occur in the real world. So, your shear force on the bottom mounts would be exaggerated, and the downwind side (downwards force) and upwind side (upwards force) of the simulated cylinder trying to tip over would be greater than what would really occur.
But, by calculating things that way you completely miss any lifting force as the wind accelerated over the top of the slightly sloping cone. I don't have the background to calculate it (maybe the aerodynamic forum??) but a section view of that lightweight looks much more like a wing-shape than a cylinder. You'll be getting less shear resistance (which creates a tipping force) but will need to worry about the Bernoulli lifting force as the wind goes over top of the cover. .
