I have read as many of the posts in the posts as my eyes can take, and I still can't figure out some of the differences between the different types of Blackbirds. I wonder if someone more knowledgeable can lay them out in one spot. From my hunting through the posts, I noticed there was a lot of helpful suggestions to various posters about which would best suit them, but not a lot of information as to why. I am about 5'11, 175. According to the charts, there are several that might suit my needs, but I can't tell the differences between them. I guess I am not looking so much for a suggestion for me(although I will take it if you want to offer one), but more for an discussion of the various traits of the choices. I am kind of a "why" guy. For example, I have figured out that if you don't weigh much, the 1.7 is "overkill", but I don't know what that means. Any thoughts? Are these different fabric weights and if so, what difference does that make in terms of comfort, lay, mosquito proofing, etc.. Thanks.