Apologies to andyb79 if my "2-5 kts above the stall" reference caused concern. In gliders, you won't be able to soar if you're not comfortable flying this slow - a common thermalling technique is to pull back until you feel the pre-stall buffet and then relax the stick pressure slightly. Every knot above the minimum possible speed means you fly a larger diameter circle, and thus fly in less good lift.
Bear in mind that (a) glider pilots are trained for this, and (b) recovery in a glider from an *expected* (more accurately in these circumstance, incipient) stall simply requires a relaxation of back pressure with no loss of height (because you're flying in lift). Even if you get caught out and stall fully (e.g. through a gust), recovery should be almost immediate with a height loss of well under 100 ft.
I imagine that someone who flies with a large lump of metal in front might want a greater margin of speed - never tried it myself.
The challenge in steep turns is flying co-ordinated - with long wings adverse yaw is really noticeable - but once you've got it a 60 degree turn is no harder than a 30 degree turn.