This might be too late to be useful, but ... I have an 1850, which is spooled with WF6F that I use for trout, on a pretty stiff 9' 6wt rod -- but not usually for Kenai rainbow. I deem it just on the cusp for that use, especially in late summer - fall. For Kenai rainbow, sockeye, and silvers I use a 1880 spooled with WF8F, on a 9' 8wt rod. Especially if combat fishing for reds on the Kenai or Russian, the 8wt setup is much more popular -- and useful -- than a 6wt rig.
Good luck to you -- and to your wife.
