Pyramids are out for me because the pole divides our shared sleep system. I've had no problems with zippers over sleeping areas, you learn to adapt. The last tent, now retired, was notorious for that, yet we used it at least 40 times in the rain, some of them mountain cloudbursts, without problems. I don't recall having a leaking zipper be a real problem in all my years of bag nights. Every design has its flaws, it's how you learn to understand limitations and adapt that makes them viable. Do you plan to incorporate a floor tub? Insect proof? Ventilation/condensation issues? True double wall, or single? Is less than a pound per person really that critical? Having spent some nights in single pole mids, I would only consider 2 pole designs for us. Double poles open up many more options than single. Singles also have a very limited section where head room is usable, unless the pole is very tall and inherently weakening the structure (and adding more material(read weight) and surface for catching wind . Also sil-nylon stretches when wet, so long planes tend to sag more than shorter panels, which may require restaking in the middle of a storm. If I chose to make DIY shelter I think the first thing I would tackle is making a list of exactly what my criteria for it was in all facets of design, then begin researching what I truly needed. Preconceptions of what works and does not, is not necessarily a good thing in deciding on a complex project. Hope it comes out great for you, a full blown 3 season tent is a pretty tough project, in my opinion.