Sorry, I cant contribute more, but I would like to toss in my 2cents about the duomid. I would recommend against the duomid for 2 person use, if you plan on using the duo-inner. We found the steep sloping sides to encroach too much on the living space to make it a comfortable two person shelter. We use the double rainbow for 3 Season, and shoulder season here in the NE, but unfortunately it's 2 1/2 lbs and not double walled as per your requests. As another poster mentioned, if you're okay with single skin, than the squall 2 almost fits the bill (2 ounces more than 2lbs, but 2 inches shorter than your desired length.
It's going to be tough finding a 2lb shelter that actually comfortably fits 2 full size adults (and their sleeping pads for that matter). Most 2lb shelters are more like 1.5 man tents, (aka palaces for 1). But as mentioned, if you're okay with 1/2lb more, take a look at the TT DR or the SMD Lunar Duo
Edit* Actually, I think Anna nailed it. I totally forgot about the LightHeart Duo. If you carry trekking poles, It's a solid bet. Not quite double wall, but pretty darn close (it's a similiar hybrid silnylon design seen in the TT DR, so you have 2 large silnylon panels that may collect condensation). Based on what I've read, I would go with this before the TT DR or the SMD Lunar Duo