This is something you might want to check .....
Victron have done some revisions to those new Plastic cased Multipluses. I don't know the full details behind it, but I think they have changed some of the cabling recommendations feeding them.
On the Multiplus 1200, they are supplying a couple of adapters that go into the +ve and -ve connectors on the Multiplus, and that will accept larger cables (which otherwise would not fit). This has increased the length of the Multiplus (maybe an extra 25mm?). I don't know if this is being done on the 1600VA model, or if it is done on the 24V model (which can use smaller cables of course) but if your enclosure is tight on space and the area you have reserved for the multiplus relies on the quoted dimension, could be worth checking?
I can't find the info right now, but IIRC, the printed manual has been updated with this change, but the on-line manual has not, so can't rely on that. I was told about this around the middle of August this year.
I would think a question on the Victron Community might get the info about this?