on a glow/gas model. over 45 is kinda nuts, imo it's getting unsafe after 50. it stops being fun and more of a look what I can do over 35. slope soarer's I'd quit about 60. with that kinda wind speed the slope face speed is going to be well over quickie speeds if not faster. a little quick for a glider, just my comfort level, more like wing stress level. there is no black and white answer here, all shades of gray and your perception of it