Well guys, I still have to wait until newborn is 1 year old at least so that we can leave him for a week with mother-in law
Regarding subframe - here is some things floated in my mind when I was planning it.
The subframe itself is seriously strong on Storm, nothing like on modern sportbikes...but consider that Givi does not recommend more than 10 kg per bag. So, taking into account that I am about 80 kg, wife are mere 46 kg + max of 20 kg luggage + let say 3-4 kg on rear rack (sleeping bags, tent) - we still well within load limits.
To make it easier on subframe I actually used Ventura-like method: rear rack bolted to square profiles, that are inserted 200 mm into subframe pipe.
Then as you see I have 4 fixation points on each side rack: 1 goes to very first half of subframe lenght, one to passenger footpeg, 1 is long stick going all the way through that welded on pipe that connnects left and right side of subframe and then 4th place bolted to rear rack. So pannier weight distributed evenly to subframe, unlike for example Nonfango system. Another typical problem - because aftermarket racks are much further apart than mine (so that for aftermarket you do not need to cut plastic) weight is much further apart from subframe on each side, meaning - much bigger effect by uneven load, crosswinds etc.
This was few things that made me do it in this rather complicated way + obviously I wanted less width. Time will tell, but I am fairly confident. I do not want to overload bike anyway, so I will attempt to stay within 20 kg limit at all costs - otherwise with pillion and luggage it will only ride on rear wheel
Good thing I have full adjustable shock absorber with stepless preload adjustment - so that I can raise rear of bike to keep handling when ride with passenger and luggage....
I actually found it more difficult to do with wingrack, but I am sure it is still possible. The Givi fitting "second subframe" you had on VFR is actually kind of what I have build out of usual side panniers suspension system, so you will have to adapt all that suspension system you took off VFR to VTR to make wingrack work.
But top box is IMHO no-go. It is way too high and too far behind pillion, so unless it is really small topbox I would not recommend it.
And - try to make welds tidy, not like mine "shaky hands" welds
You will need welder, angle grinder of at least 1 kW with cutting disks, lots of M10, M8, M6 bolts, 4 M10 spacers 30 mm long, 270 mm long treaded M10 rod - and your pillion. I had my wife coming to garage every other day to sit on the bike behind me, then I had to dismount and with her still on bike measure things
Is the sub frame strong enough to carry the extra weight 
