I have a six tier Jasper since ages and I recently added a module that I wanted to put alongside with another synth, hence the need for the holder. The holder is, as all Jasper stuff, of vert good quality and very sturdy.
One word of warning though: it is a bit tricky to add the holder to a stand with synths already in place. Since a holder can not be added to a tube already mounted to the stand, but have to be threaded on the tube, one have to tear the stand apart. I thus recommend removing all instruments before adding the holder, just to be safe.