I wrote to Hyperpro support email - got no answer. But one of my friends in Russian motorcycle portal had Hyperpro springs in his Storm so he confirmed that by "preload bush" they meant spacer
Hyperpro spring are 100 mm longer than original, and does not require spacer at all - I quite like it, it means spring can absorb more energy than short spring and spacer.
So - springs are in since yesterday evening

Had a ride to work today - don't know what to say about serious cornering with new springs, as have not been pushing hard by any means - it's just ride to work

..
First impression is strange - no dive. Just practically no dive at all.
Front feel very composed, yet eats potholes much better.
I heard quite a few people saying that progressive rate springs are bad choice, but those Hyperpso super-progressive (not 2 rates of sping, but constand change of rate along all spring) seem to work better than WP I had in previous bike.
BTW - manual clearly states that springs should go into forks closer-rate-end up, not down as stock springs...
Oil is Hyperpro proprietary 7,5 fork oil...settings as per Hyperpro: 4-5 rings out on preload, 1 turn open rebound, static sag 22 mm