I think I have the problem figured out with those Shimano L422 Light Action friction shifters on my Ironman. I forgot that the new cables came from a sketchy source. I got bulk packs of cables and housings a couple of years ago and they turned out to be mediocre quality. The cables stretch a mile before finally settling down, so I needed to pull the slack after every ride to reset the shifters so they'd cover the full range of the cassette.
I think the L422 lever pulls enough cable to cover an 8-speed cassette, which I might try -- just got a new SunRace 12-28 in the mail this week. I've had good luck with a SunRace 8-speed 12-32 cassette on my Univega for more than a year, although I need another rear derailleur to use the big cog. The original Exage RD covers only 7 speeds unless I switch to friction mode. There's a little cage pivot stop machined into the inside of the RD that I might be able to remove with a moto tool to give it room to cover 8 speeds in index mode.
And the cable housings compress so much the brakes will barely work the first few rides until the housing has compressed enough to stabilize. But I'm not replacing any housings for now, until I buy some decent stuff from Jagwire or Shimano.
I took a couple of test rides Saturday and things seem okay, although I had to keep torquing down the bolts to prevent shifter creep and ghost shifting. I'm gonna try a long ride Sunday and see how it goes.
They are nice shifters but I'll probably switch back to the original Suntour GPX group soon.