Hi there,
This is Bogdan from Romania.
I'm a mechanical engineer, designer, modeler and inventor with over 15y experience in designing, modeling and effective manufacturing of different products, devices and systems which spans across multiple industries.
What you want is a snap on system which to fit in a wide range of sizes. Anyway there will be some limitations, because the corrugated sheet will have different size(radiuses).
I could make a model for this snap-on (not associated with Snap-On tools manufacturer) which to have an intermediary component on the sheet, and the poles (corners) to remain the same. Of course will be constrained on the height - you'll not be able to have on 20inch poles 30inche (high) sheets (otherwais is possible).
So the system will consist in poles(with a specific design), corrugated sheets at different lenghts, and middle pieces (designed accordingly with the corrugation patterns). You'll have a kinda DIY kit.
If what I've sayd here make my proposal interesting for you, I think will be useful to have alittle discussion via msg board here.
Based on what we agree, I'll make a primal model for the entire system. On this system you may ask for modifications, adjustments, etc until the desired outcome is reached.
When the final model is finished and aproved, I'll deliver you the 3D model in different CAD formats (iges, step, stl, etc), 3D pdf and detailed drawings.