Start: Nov2015 -> Milestone: 13May2016 -> ongoing...
Usually you put the strings on and let it stretch to get to a stabled tension. After a month or so, take them all off and re-string at the new tension of the newly stretched strings.
In our case here, the body of the cf qin is also getting used to the tension of 7 strings; high stress. The whole body will be trying to distribute the tension evenly. Will we see any change in the skin? If yes what and where should we strengthen, the inside the outside, where to get rid of the extra "weight", over building? This will all take time; aging.
Whole thing slips - means you could play by yourself, the key would be shifted down; but if you want to play in an orchestra/ with others, then your tuning must match the others. It must be standard tuning.