I have a Solo on a Crux frame and a older Sky 5100 on a Crux frame. Both work great but I prefer the sky 5100. I run it in bivy mode( Approx same size as Solo) 98% of the time, whether its for the day or 3-4 days in the woods. The Sky 5900 look rather large to me. I think it comes down to what you strap to the pack and then need access.
Using the Solo I have no issue using it for 3 days, my setup isn't quite ultra light but I don't bring anything more than I need either. My only complaint with the Solo is it doesn't seem to get as small as my Sky 5100, Likely due to the top zipper.
Packing meat out shouldn't affect either since that would be in the load shelf.
If your near me your welcome to try both bags to give you an idea what works for you.
G