Have gone down to 150 kts in conf 1 on a very light 319. At 9 degrees pitch up attitude it is not pretty at all.
Have generally noticed below green Dot speed , you can only safely reduce speed by about 5 knots for the weights we fly. However taking flaps 1 gives a very big range of speeds and it makes sense to keep flap 1 for 180 or 170 and in some cases 160 also. However on a 3.3 degree glide path at my home base 160 in conf 1 is difficult and just about manageable in conf 2.
On 321's generally vls is more than 160 for our average weights and conf 2 is an acceptable config for a wide range of speeds.
End of the day it all depends on your personal comfort factor.