What Ph For Cloning W/ Rockwool

I usually use plugs and have only cloned using rockwool once. When I pre-soak the cubes, what should the Ph be?

everyone seems to reckon that you need to pre soak the cubes in something like phosphoric acid treated water at a ph of about 5.8, but for cloning i dont bother to pre soak i just water with ph 5.8 water and stick the clonex'd clone in, i dont use special little cubes either, just chunks chopped off a big piece, the temperature is important must be over say 75 or they will take ages, you do not absoloutly need a humidity dome as long as you can keep cold drafts away from the clones and the rockwool damp, just spray/mist them everyday. people recommend feeding with dilute nutes and other additives, dont, you want the clone to put out lots of roots looking for food, if the RW is full of food the plant will be less inclined to root as fast.once it has rooted then you can feed it. PH should be between 5.5 and 6.5