This segment describes "Fitch Variation" of Sawback Trail between Mystic Junction (FM19) and Flint's Park (CR31).  On my visit, according to overall strategy, I made a "basecamp" at FM19 then dayhiked with light pack;  this gave me plenty of time to explore fantastic - and not quite expected - Forty Mile Summit and beyond Alpine area.   There are two major highlights situated at opposite sides of main corridor - Sawback and Rainbow Lakes.  Most Sawback backpackers simply hike through missing both, and that is the shame due to extraordinary beauty and overall remote feel.   After hiking to Forty Mile summit I made a loop:  First visited Sawback Lake, then looped back via lower Rainbow Lake Connector and back to Forty Mile as shown on following two maps:

Section between FM19 and Forty Mile Summit is ~6.5km and mostly forested.  There are two trails: Horse that stays lower mostly following the creek, and Hiker Bypass on east side.   Horse trail should be avoided by all means as it is deeply rutted and has many non-bridged creek crossings.  However Hiker Bypass was not smooth sailing either, with many fallen trees and collapsed bridges;  apparently Parks Canada is not maintaining this trail anymore.  There were also large amount of huge frogs on trail the whole day and it took real effort sometime not to step on them, as they moved quite slowly.  Hiker and Horse trail rejoin ~1km before Forty Mile summit; extraordinary alpine meadow ~2km long.   Upper Rainbow Lake connector splits on the east side roughly halfway along the meadow. It is not signed and easy to miss - see last photo in gallery.  Trail then descends steeply ~150m vertical and crosses Sawback creek on good  bridge to junction:  Sawback Lake left in ~2km, Flint Park right ~4km.   CR31 campground is halfway to the lake and would be great base to further explore the valley. 

After visiting Sawback Lake I dropped ~30min down Flint trail to lower Rainbow connector.  Fallen park post missing sign was yet another example of Parks not maintaining this area anymore.  Rainbow creek crossing is directly below and there is no bridge.  Hike to the lake will take good hour, but it is very beautiful mostly on semi-open escarpment with great views to the west - see gallery.  Eventually it merges with upper connector by big larch few minutes before the lake.  Rainbow lake is extraordinary, to say the least.  There are larches all around and it would make great late September destination too - only if it wasn't so far.   In 2015 Parks Canada flew batch of Westslope Cutthroat trout from Sawback to Rainbow Lake, attempting to preserve this fish species native to Banff National Park.  Ridge above the lake on south side begs to be hiked;  it would provide great views of Mt. Sira, and looking at maps one could probably descend on the other side to next valley south which contains yet another wilderness lake, likely never visited - so much room for exploration.  Upper Rainbow connector to Forty Mile summit is shorter and after couple of switchbacks gradually descends to main trail ~45min from the lake.

Backpackers making through hike will have some logistic issues visiting both Sawback and Rainbow Lakes.  Most practical approach is probably to stash heavy overnight pack at Forty Mile summit, then hike upper Rainbow Connector out-and-back.  Same strategy can then be used at Sawback/Flint junction for visit to Sawback Lake. 

Sawback Creek Sawback Creek looking towards cirque that holds Sawback Lake, ~2km away