I bought the Shad 48 because match with the width of the bike... ample storage, but if you have more budget get the Expandable one.. since the lid for the 48 is quite low ... (cant put anything else on the top of ur helmet)

its z650. Yes, same rear light as z900.

vs is super comfy. words saying that it rode like you're sitting on a sofa.

I'm not into top box, panniers are enough. But I neet to cover my wife's ass so I'm looking a small box for that purpose. Pelican seems to be a good choice but the price is killing me. Any advise, does shad come with small boxy type.

actually it depends on your bike, wether Shad is bringing them for your bike model or not.

See below example:



But that is with the Daviel as an example.

This is mine:



with Shad 39 & fitted with backrest (my wife is loving it)

Did the box ever try to shake the bike's tail at high speed?

I can still reach >150kmh but that is not through/while a long journey though. It was a few kms stretch. Couldn't tell it is not shaky, but i don't feel that obvious 'shaky'. Its sturdy, but maybe you can feel a little bit of resistance/drag due to a box behind you trying to break the air resistance as well. My bag weight is about 2-3 kgs is always with the box when i'm riding.

Givi or any boxes are know to fell off the rack, I suspect of heavy loads. When you hit a bump or slammed the bike hard enough they might fly off that bracket so put things lightly. I've had couple of times my sideboxes popped open or fell off because of weight. The tell tale sign is the loose fit when the box is locked in place. There may be temporary fix but as it wear off the problems come again.