Roofracks... How to best access the roof?

[GadgetMan]

I would like to fit a roofrack to my SWB Mid roof VJ

On this I would like to fit a streamlined storage box, for my Kites and KiteBoards (I'm one of those mad blokes who Kitesurf)

how strong is the roof? would a factory ladder on the rear door, and some Alloy Checkerplate along the roof be sufficient to access the box?

It needs to be accessed on the side, not the rear unfortunately, and I'd prefer not to have to carry a stepladder if possible.

Any Ideas?

heres an Idea of what I intend installing on the roof...

http://www.roofracksa.com.au/lugbox.php?page=thule&model=X1

Cheers

G