I have been to this cabin twice but have never been willing to tie up out in the river due to the current. The lake is also called Figure Eight lake and is two separate lakes. Some maps show the lakes are connected but in 2010 the gap between the two was not open. At best you have about 1200 feet which makes it impossible to land for most planes. I would drop people off by landing in the river but would not leave my plane tied up in the river. Your passengers would have to be strong to deal with the current.
Link to Forest Service site. http://www.fs.usda.gov/recarea/tongass/recreation/camping-cabins/recarea/?recid=79213&actid=101
Link to Recreation.gov to book cabin. http://www.recreation.gov/camping/Twin_Lakes_Cabin_Ak/r/campgroundDetails.do?contractCode=NRSO&parkId=71895&topTabIndex=CampingSpot