Just took a look at that on SA’s website - interesting design. I already have the 50lb Lazar spooled up, but I will keep the SA Flat in mind for my next rod. Getting into Spey/Micro Spey and skagit lines has been a blast. Spent Monday using an OPST line with an integrated running line on my single-hand 9’ 5wt rod, swinging and stripping small streamers for browns. In comparison to my conventional, overhead casting setups the skagit line makes casting the heavy flies so easy and enables casting in some tight spots.Go with the 40 lb line. Consider the SA Absolute flat mono shooting line and save a bunch of money.