Hi JT:
35'/15' min when wet, FAR 25.111(c) (2), 25.113 (a)(1), and 25.113 (a)(2) (all engine...) alternatively CAO 20.7.1B, Para 7 (had a nice discusion about wet screen in the past...). FAR 25.113(b)(2) covers wet for the Gringo's... 15'.
50' does crop up in other matters... (various ICAO docs re procedures...) but not screen height at end of TODA.
cheers, and happy METO settin'
FDR