In the lingo of the day, 28t max meant the biggest possible cog you might get away with on your freewheel, not total tooth capacity.
Honestly, that looks dangerous. A chain that short could fold the rear derailleur into your wheel. You'd be better off adding some chain, and losing another gear combo with the 32t. That's kind of a hack though.
I suggest you get one of those SOMA Spence Wolfe style extender cages if you want to run a triple. A super record RD simply is not designed for that. Typical gearing would have been 42/52 and a 13-21 in back. Maybe a 13-24 for those epic climbs or for those that preferred to climb in the saddle most of the time.