MLS-12D
I have never seen a glider whilst flying an airplane
I was just about to ask which universe you live in; then noticed you are in Canada
I see countless gliders, everywhere up to say FL060.
Flying low is the worst advice for GA traffic; most of it is already below 2000ft agl and most military low flying is done there also. The higer one is, the less traffic there is, the better service one gets from radar units, etc...