My official vote: DMC/Item. And I'm not strongly attached to fractional spending of DMC for commissioning so I'm just as happy to let that be full DMC only.
We do have a precedent for justifying .5 DMC used. That equals 30 days which the same increment you can get for TBX/TBG. Either way, tracking is not an issue on the Wiki. It sounds like .5 DMC for commissioning might be a compromise of a sorts.