Hi Martin,
I am really glad to see the rush to use the Advanced DSO feature, but we have to hold our urge.
To use advanced DSO the prerequisite is 1.5 (or higher) of the BW Modeling Tools. BWMT version 1.5 is planned to release in Oct 2014.
And also its recommended to use the Advanced DSO option in SP09. It is however possible to apply the necessary corrections via SAP notes as well on BW7.4 SP08, but contact SAP to do it.
I hope this clears all your doubts.
Thanks & Regards
A.Dinesh