I agree with R Carver in that full crow (that is with the ailerons full up and flaps full down) causes too much loss of axial control. At least with my sailplane I much prefer full down flaps (90 degrees) and neutral ailerons. It slows the ship beautifully and I still have full control. Full crow does look kinda neat though! I've tried it all different ways and personally prefer neutral ailerons. This may vary from design to design though.