What I was trying to say-very poorly, hehe- is that 15 or 16 is WAY too small and it's ludicrious for someone to suggest it!
Track frames have taller bottom brackets, shorter chainstays and steeper geometry. But you should be within that 59cm with respect to the top tube length.
For example, if your track bike has a 59cm TT/ 10cm stem = 69cm total. So your mtb or ss should have a reach of 69 or a couple cm less.
You won't find that with a 15 or 16" frame. More like a 19 or L or XL MTB frame. Alot of mtb are measured in inches so you might want to go over your track bike and measure in inches to get some ideas.