Hello Funkyotter. I see no one answered your post... Perhaps I can get the ball rolling. to the forum!
Unless you are very tall, 43" is on the high end for height of a layout. Especially if it is deep. My standards are 40'' high and 2 feet deep max (from reach), especially if scenery building is in the books.
The height between levels will depend on the depth of your layout. If it is deep, you will need more space between the layers. Here is a thread of interest:
https://cs.trains.com/mrr/f/11/t/201296.aspx
Simon
Have a spare room now in the basement. Space is limited with desk and display cabinets . Built a n scale table ( inspired by Red Oak layout). Tempted to cut the legs though, current height BEFORE foam is 43 1/2". Reason for this? I really want an HO scale shelf switching layout too. I just want it all :))) it would have to be built above the table though. Obviously there would be a problem with adequate space for the scenery backdrop and terrain elements. Does anyone have a similar setup? I suppose this could be approached similar to a multideck arrangement except in this case the two are really independent of each other. Different scale and theme. Thanks!