Up until now I've been riding a CBF125 and it came with a topbox when I bought it, which has proved itself very useful as I carry an almax chain (quite chunky) and a lot of other stuff. It's quite a small box, only fits one helmet and it can be a tight fit for my other stuff sometimes (and I'm not sure what literage it actually is).
I should be changing soon to an ER5 and I'm wanting to order the rack/plate/topbox or whatever is needed but I'm slightly confused by all the different things I need, and just wanted to make sure I actually order the things I need and ones that do match :) - which is why I thought I'd ask you guys for help.

I've been thinking of getting a larger topbox as well (45/47l maybe?), but I've never actually ridden with a bigger one. Do they affect balance much or cause any other problems, whether when filtering or travelling on the motorway or so? Any wisdom is welcome :)
Now the thing I've been confused about...
http://www.motorbikesandparts.co.uk/giv ... 16654.html
This rack is meant to fit the bike... and as you can see there's an option to also order a plate.
But then, you've got this http://www.motorbikesandparts.co.uk/giv ... 10476.html which says it's got an universal plate... so I'm just slightly confused on whether I'd still need to order that monolock plate when buying the rack or whether it comes supplied with the topbox itself?
Could someone explain how it works or what it actually is I need to get it sorted?
P.S. Is there realistically much difference between 45 and a 47l top box? Unnoticeable or just enough to make the difference when trying to fit two helmets in for an example?
Much appreciated!