Mountain bikes seem to be easier to morph to a usable size (not too big...just ranging on the small side).
I have ridden 15” frames comfortably up to about 20/21” (likely my “true” size).
Larger seatposts, angled quill stems...
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1987 Crest Cannondale, 1987 Basso Gap, 1992 Rossin Performance EL, 1990ish Van Tuyl, 1985 Trek 670, 2003 Pinarello Surprise, 1990ish MBK Atlantique, 1987 Peugeot Competition, 1987 Nishiki Tri-A, 1981 Faggin, 1996 Cannondale M500, 1984 Mercian, 1982 AD SuperLeicht, 1985 Massi (model unknown), 1988 Daccordi Griffe , 1989 Fauxsin MTB, 1981 Ciocc Mockba, 1992 Bianchi Giro, 1977 Colnago Super, 1971 Raleigh International, 1998 Corratec Ap & Dun, 1991 Peugeot Slimestone