I changed (well, started to change) about eight years ago. Lots of changes at the time, all thought through carefully - bee space, box size, OMFs and brood frames (to Hoffman).
I was much at odds with almost all of my colleagues at the time but as it has turned out, more and more have followed suit since. Once changed, never (well, never, say never) to change back (it may be better to say none, that I know personally, have changed back to standard brood, bottom bee space, or to solid floors).
The only down-sides as far as I can think at this present time is the frames are very marginally harder to extract from the broodbox (lower down by about 7-8 mm) and when standing a box on a flat surface, the combs are often (well some, sometimes) pushed up due to comb on the bottom bars. Initially, the cheaper slotted Q/Es were changed to framed, and eventually to wired, as they sagged in the centre and stuck to the frames above rather than the brood below at the outside and were glued both ways in the middle! Oh, one is more carefull when standing a box on a flat surface as possible contamination is more likely.
Advantages.
Bees always go up so bees with heads above the frames are still safe from decapitation when replacing the boxes 'on a skew' and slowly rotating into position, while there will be very few hanging from the frame bottoms, so that problem reduced, nay, eradicated.
Crownboards are now simply square pieces of 9 mm ply - I changed from 6mm to 9mm as my thinner ones were too flimsy and prone to warp (without a frame). I have not had trouble with the thicker boards yet. They are stored flat.
(Almost) all my kit is now top space, I think. It takes a lot of concerted effort to change when there are a lot of pieces of kit in use - broods, supers, Q/Es, crownboards. Part of my problem was I was comparing the two -side by side - not knowing whether I should change or not; there followed a period when I was no longer spending enough time at home (family reasons) and my colony numbers contracted somewhat, so I had plenty of spare kit without altering the last few boxes. It has now changed.
When the first Dartington came along, that too was top bee space, so matched the rest (I use National supers on my Dartingtons).
The main problem in the future, as I see it, may come if, or when, I wish to pass on my kit. It would be out of step with most other National owners - at present. I am not going to worry about that one, though. Changing back is less difficult than converting - just a 7-8mm strip of wood (or other) onto the frame ledge - yes, I know the frame runners might be more of a pain, perhaps and the clearance over the frame lugs would need to be restored.
When you look at the 'rest of the world', ie Langstroth, they are top space. I know not why the British Standardisers went for bottom space in the 1920s. Maybe there was a compelling reason? I doubt it, more like appeasing some of the 'then suppliers'. The only advantage seemed to be the queen excluder and that may not have been a slotted sheet in those days.
Regards, RAB
