Originally Posted by HillRider

You can safely violate any rear derailleur's published wrap capacity if you are careful to avoid using the small chainring(s) with one or more of the smallest cogs.

As to chainring gearing, the smallest ring is defined by the crank's bolt circle diameter. A 130 mm crank can fit a minimum of a 38T ring and a 110 mm can fit a 33T as the smallest.

I've heard of TA cranks being fitted as 52/28 doubles. I'm sure the shifting wasn't terrific but with friction shifters and by anticipating the shifts you can get away with a lot.