1. If I understand correctly, a double sided panel has stiffener webs on both sides of a skin.. so the panel is essentially symmetric about the skin.
HyperSizer currently has no real way to do this. The best approximation I could think of would be to put in the ribs on one side and then double the height. Then you would need to restrict the panel against bending. If you are integrating with FEA loads, then you need to check the box on the FEA tab that says "Zero out FEA Moments". THis means that HyperSizer will ignore any bending moments coming from the FEA analysis and will apply constraint against bending in its place.
This is not a perfect analysis, but should get the right object loads and panel membrane stiffnesses. The biggest drawback I can see to this is that your web local buckling will be considerably over conservative (because your ribs are two times too high). You can account for this by either allowing a buckling margin of safety in the ribs below 0... or alternatively specify a "local buckling knockdown" factor of > 1... perhaps 1.5 or something like that.
2. Cannot directly model the periphery as part of the panel, but if I was doing this analysis in FEA, I would model the periphery using beam elements and then in HyperSizer size these elements as a beam component.
