Make sure when you dry fit that the front baffle sits flush with the sealed boxes. Mine was close without glue, but left enough lip to hang a nail all the way around with the glue taking up space in the gap. I should have tried to make adjustments prior to glue up, because I didnt go a great job of fixing the issue afterwards.
It would be better if there was enough leeway in the dimensions where the sides and tops would overhang the baffle and back, where you could just run a flush trim after glue up and have a perfect fit. I just put a finish over the MDF so it didnt cause any real issues for me (largely since I acknowledge that although its not a perfect cabinet, it turned out better than what I would have made myself), but if you are going to try and veneer the baffle be sure you are happy with the fitment before you start gluing.
You will also have to add a strip of wood at the top of the front baffle between the boxes as the baffle isnt full width there, unless you are adding another layer over the front baffle. I had some issues with my strip soaking up too much shellac during finishing, so use caution there as well.