I think it is very possible to hit that speed especially on that stretch. your cadence suggest a 46.6mph you can check it here.. ...http://www.machars.net/bikecalc.htm. I know I have hit over 50 numerous times on many computers over the years.. I have even been in a draft on flats and hit 50 confirmed by the driver of the truck.. I think my fastest was 63.3mph but i don't believe that one... I was never abel to reproduce it..