The ratchet adds drag to the line holding power. I can't imagine the need to have two ratchet sheaves. Too much drag possibly. You also risk having the ratchets on or off at differing times. I would rather have control over when they are on or off.
Having an upper and lower ratchmatic will negate the need for the cleat totally. It is sometimes used be serious racing crews on modern boats to allow constant fine tuning of the mainsheet with very little line pull when not trimming. The same trick with double auto ratchets is used on spinnaker sheet, almost universally by now and it works great there. No trouble with ratchets turning off and on a t different times as they simple won't do that. The top ratchet will always engage before the lower one and disengage later.
The difference in sustained static holding power is massive. You go from about 1:6 on the partly wrapped lower ratchets to 1:60 of the combo. It will almost feel as it the sheet is in a cleat. But when you push the sheet towards the blocks then the line will run through the mainsheet system rather quickly. You'll have to use AUTO ratchet for both blocks otherwise it won't work well.
Wouter
