Don't forget, there is no real number for all conditions. Smooth air and rough air, small thermals and big thermals all require differnt speeds and bank angles. Its true that you should have some referance but I have yet to find that one can just fly by the numbers... use your perception and feel what the glider likes the best. If your to slow, you will know it and because of the sluggish responsivness and if your to fast, you will keep losing the thermal. Point here is tune into your own perception of what speeds are best to fly.
As a note for better performance while thermalling, use a little outside rudder (i.e. if your thermaling to the right, use a slight amout of left rudder). This takes practice and is not intuitive but the ASW15s seem to climb better like that. there was an artical in springs Soaring magizine that talks about this... it works!
