So currently we have two shipping services with two rules for each (Small and large parcels). They both take into account weight and dimensions.

If a single small item is ordered then it will fall into the 'small rule'. However the problem comes when more than one is ordered it still remains in the 'small rule' as the total volume is not taken into account only the weight. If the item is really light but has a big volume it won't get changed to 'large rule' as the weight is still applicable to 'small rule' but the dimensions are far to big for this rule. 

I need the max dimensions 'volume' to be taken into account as the only current way around this is to play with the weight however I will be charging far to much in postage for this item if I start to change the weight. 

If anyone has managed to find another solution for this please let me know.

Thanks