Rooftops,
I don't need, or want, the dividing board. Never too keen on 3 frames except in really warm weather - almost gives me visions of of an observation hive format. I might change, but......Good job we are not all alike.
I think the bees would rather have a symetrical (spherical) nest even in a polynuc, so that is what I give them at least as starters.
6 frames is a good size for a bit of brood expansion, ready for a full 14 x 12 box. I always prefer to be generous (with bees) in nucs - they build up so much more quickly.
That blocked off entry will not be a problem as I could always remove the infill and cut an opening and cover if required, but the styrofoam type insulation boards i have used may not be robust enough if things get too propolised in that configuration. May need some inserts to do the job better.
However, these nucs look to be very adaptable, and apart from being ~100mm longer (than necessary) for a 14 x 12 nuc, I am more than well pleased. They just looked big when I first put them together! But are much lighter than my wooden ones when the coverboard and roof are added.
I am now thinking of ways to feed over winter, if required.
Regards, RAB