Needs to be one of the big ones 500L+

Also needs to be minimum of 170cm long (195cm ones preferred)

Something along the lines of this:

http://cgi.ebay.co.uk/Roof-Box-Large-Halfords-580L-Roof-bars-ford-S-MAX_W0QQitemZ320515614684QQcmdZViewItemQQptZUK_CarsParts_Vehicles_CarParts_SM?hash=item4aa03827dc

I fear that may be too big.  Also, its own weight has to be taken into account - max 100kg for omega roof - you need to include roof bars and roofbox in this value, as well as luggauge.

You just need length?  What about the long, thin 'ski' type ones?

TheBoy wrote on 13. Apr 2010 at 22:02:

I fear that may be too big.  Also, its own weight has to be taken into account - max 100kg for omega roof - you need to include roof bars and roofbox in this value, as well as luggauge. You just need length?  What about the long, thin 'ski' type ones?

Seen those, but thought rather go for the bigger ones to get more stuff in  :-/

Length is the key for boards, would like to get other stuff like Ski & Snowboard boots in on top too

Still think its too big - remember you cant space the roof bars more than about 40-50cm apart ;) - so with the amount of overhang, thats a big ask

would need to be at least this size...

http://cgi.ebay.co.uk/halfords-roof-box_W0QQitemZ320515913534QQcmdZViewItemQQptZUK_CarsParts_Vehicles_CarParts_SM?hash=item4aa03cb73e