I hear that there is a profuse review on the Numlus Soaring Supplies
site and a 190 page manual written by the servant.

After extensive testing, I have found that the closer the MKIV is
mounted to the front of the canopy, the more sensitive it is to slip
and skid, probably because of tighter radius of curvature of the
canopy. I had to install four, using the one closest to the horizon
for whatever speed I’m going since I want more sensitivity at slower
speeds. With + flaps you have to remember to watch one higher than
the one at the horizon to maintain sensitivity calibration.
Fortunately, at full flaps on final you don’t use the yaw string much
so it isn’t necessary to make sensitivity compensation.

AGL