Originally Posted by
noglider
Not that you asked, but I've been doing the opposite lately. I have a bike with 10-speed indexed shifting and am using a 7-speed freewheel. I'm surprised at how well it works. Sometimes I have to double-click to get one shift, but it's OK.
Likewise, I am temporarily running a 10 sp dynasis Microshift thumbshifter on an 8sp cassette and derailleur. There is only one double shift in index mode (in the middle of the cluster). In friction mode its all dandy. FWIW, the dynasis thumbies have a larger diameter barrel, almost like the XT thumbies of old, larger than the smaller diameter Suntour types.