Thanks for the input everyone.
With regards to not having an end result in mind - the end result, is to have equally good street shots at 50mm and f8-16 that i get with my f1.1, but without the excess bulk, at times when the f1.1 is not the primary purpose of using the lens (which very often, it is). Sometimes i'm street shooting with zone focus, sometimes i'm picking out subjects with fine focus and high isolation - one can have more than one style of shooting given differing circumstances.
Based on what i've seen from the various photo examples and the shots of the lenses on the camera, i'm not going to be saving much bulk over the f1.1 and i'm unconvinced that the Summarit offers anything "special" in terms of optical character.
Therefore, i don't think either of these lenses are what i'm after in a 2nd, compact, 50mm lens, and in fact the CV 50mm f2.5 is the way to go for ultimate compactness when in zone-focus street shooting mode.
It's been very useful everyone, thank you for taking the time to give me your input 🙂