My D-18 is fine on 12s, and my hands are happier.

I used 13s on both my Martin Dreads for years until the arthritis and Tenosynovitis made it too painful, and I dropped down a gauge. Once I got the relief sorted, no problems, no loss of volume that I’m aware of, and they both sound ‘livelier’ (as In, they ‘have more life in the sound’). I occasionally put a set of 13s on them to check that I’m not deceiving myself, but they make both guitars sound ‘choked’, less ‘life in the sound’ to my ears.

But, as we constantly say, to each his own!