Stratospire 1 vs Stratospire 2

No because you are already taking an 8oz weight penalty by choosing the SS1 v.s. the Notch.

; )

You are asking the wrong forum if you want a yes answer. I was thinking of an SS1 fly with a new inner for 2 people. The SS1 is big enough for 2 already. The SS1 I think will fit a smaller footprint for tight camp sites and be more windworthy than the SS2.

It depends on how spacious you like it, but to me an SS1 is a solo tent and and SS2 is for two people. Both provide plenty of room for what they are designed for. An SS1 can expand for 2 in a pinch, and an SS2 can expand for 3 in a pinch, but I wouldn't use them that way regularly unless you like to camp like a sardine. Also, for those of us that like to use a 25" wide Neoair, it negates the expansion possibilities (and thus the reason I won't consider a Notch unless I go back to a std. 20" wide pad). I have both an SS1 and an SS2, and I really like the spacious design of this tent and the lack of poles in the sleep area. If you get a good taut pitch, it does just fine in most windy conditions, especially with the outer tarp fully zipped closed, but I have yet to test it on a ridgeline at altitude during a storm.

The SS2 is overkill for solo trips. Heck, the SS1 is huge for solo trips. Best consider the SS1 a "1+" shelter and the SS2 as "2+". If I was going to use my SS1 to accommodate another body, I would simply do so without the inner.