I think you have a good plan here Hoco. I have messed around a bit with changing strut lengths from the ideal and never had any problems.

I built a couple of tensegrity octahedrons where one side of the octahedron was about 16 feet and another side just 4, in order to get the shape I wanted for a sort of cantilever support piece. These did quite well out on the playa 3 years running.

I modified the strut lengths for a 2 frequency octahedrally based dome less radically than that, to fit the struts I had available, and again, it was totally solid.

The only thing I would keep in mind based on my experience is that longer struts are "weak" in the middle, if someone is stepping on them, or will be liklier to deform if put under a lot of compression load, which can happen when you deviate from an ideal structure-- the load won't be transmitted as evenly to all vertices.

I built my modified 1v this weekend and I ended up making the top pentagon the same size as the floor pentagon. I used 10' struts (e.g. uncut EMT sticks) for the top and bottom pentagon. I cut 8' 3" struts for the sides (then pressed them and drilled 1" from the ends). This made the vertexes around the top easy to reach but still overhead. I made the top five roof struts (that meet in a peak at the center) 9' long.

The result is a dome about a bit bigger than a 2v optimal dome, with more vertical sides. I can put it up in a few minutes, without a ladder (I attach the five roof struts together first and then attach them to the top pentagon second, so I never have to reach the top vertex). It has natural door openings -- no need to duck when entering. Plenty strong. :-)

The struts cost me about $150 as EMT has gone up to almost $6/stick.