Quite some years ago now it was me who specified the detail of the ones currently being retailed by CWJ, which were a joint effort by two Danish concerns and myself. From the start the focus I insisted on was compatibility. Compatibility with wooden components that is. Same external dimensions, but full insulation value, hence the one frame less situation. It works just fine although the design does have some shortcomings due to it being the first one and there being no certainty the very conservative UK market would adopt it, and thus we were not going to throw unlimited money at it.
Compatibility is what gives you free choice. Some of the non compatibility issues are accidental. The maker arrived at their own solution of how best to do a poly National. Some compatibility issues are deliberate. Once they get you onto THEIR pattern you cannot change to that of another maker without having issues, well pointed to by itma below.[/COLOR]
For poly Nationals, the principal problem for me is that there isn't a standard, and you are closely binding yourself to a single supplier.
Thats pretty well the case for all hive types actually. Its a lot simpler in a hive with short lugged frames though, and the UK penchant for long lugged ones makes things a bit more awkward. The market for Langstroth for example is now pretty mature and, apart from fringe trade, has polarised down to a couple of basic variants, the plain jointed or the lipped versions. Both have their adherants, although I understand that the plain outsells the lipped in most markets quite comfortably.
In time a standard will emerge by itself, a pattern becoming the dominant one and the others will fade away, and any maker not using the standard favoured version will find themselves with a minority market.
And that's before we get to aesthetics, environmentalism, toughness, need for strapping, etc.
A strapping point has been included on the migratory version floor we had made. Remachining his to accomodate whole floor mesh would, however, be a big issue. The static version of the floor (borrowed mould for a Swedish national actually) is very easy to modify, and could be made that way at a relatively modest cost