We currently store the IPA domain SIDs in the extraSIDs part of the PAC. This part includes full SID for each identifier. We should probably investigate putting these SIDs into the ResourceGroupIds instead (One full domain SID + N 32bit RIDs) which is more compact. More reasearch into further SID compression is Needed. Sid Compression is mentioned in MS-KILE
Metadata Update from @simo: - Issue assigned to someone - Issue set to the milestone: Future Releases