I am not a rescue - (although it feels like one at times:lol
but thought I might just add in a thought or two having rehomed from many different rescues and also done homechecks.?
The height and size regulations are designed to be a minimum, but also are designed really with the 'old fashioned' style of housing in mind. (hutch and run) and a standard twosome.
This leads to difficulties interpreting them when faced with different style housing -
For example I now have smaller (aviary style) runs than I used to have, but they are now equipped with fully covered insulated rooves, and have raised built in 'hutches' accessed by ramps with flat spaces on top of the hutches also accessed by ramps. If I were to measure all the accessible spaces (floor, hutch floor, flat top to hutch, x2 very wide ramps) it ends up as the same space as before (and more sheltered and variable and entertaining) BUT on the basic measurement of the floor space of the 'run' alone its only 9ft by 6.6ft. (total accessible flat areas total 16ft by 6.6ft plus the two wide ramps)
None of this space is taken up by the large holes that you get in the floors of 'two up' hutches (which personally I find a waste of space) - which is also a factor.
However one rescue was reluctant to home to me at first because I did not quite reach their minimum of 10ft by 6ft basic run space and they did not wantto be seen to break their 'rule'..
Heightwise I feel personally that the full stretch up of the bunny (not just periscoping but actually standing up on its hind paws stretching up the wire as if 'stood up' should be measured as that allows bun to really stretch its legs and spine.
However again that leads us back to who is making these now and the expense?
The only 'traditional hutch' style accommodation that I have ever felt happy with (and then only if run time is allowed) is the Forsham Very Large Hutch (7.5ft by 3ft by 3.5 ft) and they are now sadly bankrupt.
And what do you do with foursomes? All mine are in foursomes and I personally do not feel that this needs twice the space of a twosome (they tend to lay in heaps anyway!!!) as the space if for running etc. But I might feel differently if it was a hutch style accommodation.
Just to add that unless it was a very small nethie I personally would not be happy passing a homecheck with an 18inch hutch - its like someone living in a 6ft tall room!
Sorry if this just adds confusion.
.