Got all my circles cut and have even inserted the end pieces----thanks to your suggestion to hammer them in place from the opposite ends. Will take some photos as soon as my son returns my camera. One thing is clear though; sonosubs are way easier to build than regular boxes!!. Far less weight, no internal bracing needed, and way easier to move around by yourself. Couldn't move my Marty without help. If there are no performance related downsides, and provided you have the height to accommodate them (if you are going LLT style), I am surprised we don't see more sonotube builds around these parts.
I always felt the same way about them being easy to build and maneuver. The circles are a bit repetitive and time consuming but they're not hard to route out. I also think they are more stealth for corners.
^^^^So true about the repetitive nature of cutting those circles---having to make 3 or 4 passes for each circle is brutal---and the dust----fugedaboutit!. But once you get past that stage, it's all downhill.
If you don't like the multiple passes with a router, try something like a Rotozip. I made my sonotube sub many years ago using a Rotozip and a homemade circle jig, in one pass for each circle. My Adire Audio Tempest sonotube is still running great!