I just changed one of my 2 guqin's strings to the Tobaya silk strings. It works as some reviewers on the internet claimed. When first mounted and still untuned the thickest 1st string was already at C-sharp. I had to pull the 1st string a few times to lower it to C-flat, so that I won't have to tune the thinnest 7th string too high. Over the next week or so it should settle to B-flat on its own. The Tobaya strings feel very 'slingy' in a very good way (to me anyway). Overall I would say the Tobaya silk strings (only one standard gauge) feel like Taigu silk strings (standard Taigu gauge) and sounds a bit even more trebly than Taigu strings and in my personal opinion that's good because it can 'cut through' the cacophony of noises in my lively home environment with kids running around, windows in my living room open, MRT subway trains noisily plying the tracks beside my apartment block. Haha
As you can see in the 2 pictures below, the metal-nylon strings that came with the guqin have left some permanent marks in the 'dragon gum' of my guqin. Silk strings, by contrast, won't leave an indelible mark on a guqin.
All the old JinWu brand strings were removed.
The new Kyoto Tobaya silk strings were mounted onto the guqin. The whole process took about 1 hour at a very leisurely pace.