I'm going to guess that it's mostly in the shifter. If you have a bar end shifter I'd stick on whatever you are comfortable with. If you're using STI shifters, you'll need a road bike derailleur so I'd try the Ultegra. Most of those derailleur specs seem to be pretty conservative so I'm about 90% confident it would work. I'd have no concern whatever about little/little performance or even slack take up because I only use my granny chainring with the largest 2 or 3 rear cogs.
My newest recumbent bike has only a 20 inch rear wheel so I have a 60/50/39 triple crankset that shifts perfectly with an older (1995) XTR front derailleur and a bar end (friction) shifter.
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