I'm not 'promoting' anything. I replied to a beginner's (JBG's) remark about a specific space in a BHS hive. My reply was based on my experience of managing that hive. From your posts it seems that you don't own BHS hives, so you don't know.
Yes - the discussion has veered between BHS and Swienty (old and new) and comments about the different things have been confused.
I have understood you to be saying that a 1mm gap on the old Swientys prevented propolisation. Which I find very hard to accept.
I have a BHS floor(which I'm not keen on, but have never seen any evidence or even possibility of the problem with which JBG started this thread) and their roof and have been considering buying some BHS supers (even at £25 vs Paynes sale £15ish).
Hence I am keen to learn whether or not this would be worthwhile.
... One fault is that although they are bottom bee space there is 4/5 mm gap above the frame to the top of each BB / supers. …
If this comment is true, (and its new to me, just like his entrance problem) it sounds as though the BHS boxes (perhaps like the Modern Beekeeping Langs) have a half top-beespace.
And, if it is true, that would make for an overlarge beespace (and thus brace comb) when a BHS box was used under a standard bottom-beespace box (wooden or Paynes) with the 'proper' bottom 'cut-out'. Similarly, putting a BHS box on top of any 'standard beespace' box sounds as though it provides no beespace over the lugs, inviting propolisation (the specific problem with the new Swientys).
I'm very keen that ALL my kit should be as inter-operable as possible, so, if this is true, I'll be getting my extra supers in Paynes sale.
Do the BHS boxes have the half top-beespace reported by JBG?