Alan, I agree about putting steel string on your Martin. Nylons are easy on the fingers but they haven't the power to drive the top correctly. If you can't handle steel strings on you finger tips yet, at least go to Silk and steel. You maybe damaging the guitar by not having enough force on the neck. That Guitar will handle medium gauge strings but I also agree with using lites. I like Martin Bronze or Marquis, if you can find them anyplace Darco New Yorkers were my favorites. My brother has a 00-18 from about 1960 which he plays a mixed set of GHS strings on, heavier than lites , not quite mediums.