Based on 57 yrs and over 1.5 million miles in many parts of world, you don't want anything higher than GIVI box---kind of like adding
a rock to back of arrow.
My GIVI box E47 has over 500,000 miles and still functions for dog to ride in,
Rack on top, maybe not great idea---I will leave that to the look thru windshield, highway peg types who probably don't feel handling reduction
Remember GIVI box is clamshell design---another excuse for stuff to slide out when bike on side stand. Better is plastic tool box, yellow, bolted to spoiler,is not clamshell......and of course much cheaper, requiring no rack
For my SilverWing and present new Burgman 400, following great, cheap idea for scooters with hinged seat. Aerostich#948, Seat Hooks @$15, probably cheap mail to UK, Japan sourced. These clip to side of seat, a tiny self tapping screw can help keep them im place. Bunge rubber bag to seat, these allow seat and its under storage to be opend without taking bag off seat. Use stick as prop. Work great!
In my second retirement I was living off bike for 6 months each year. You travel lite and find a lot of junk un-necessary. Fun. Scooter/motorcycles can carry a lot at least for short/slow disstances---one 15 yr period I tried to buy nothing I couldn't carry home on bike...or have car. Great life=no wife, shared expenses.