You loose the bottom port (of the three) on the straight & corner, but all the rest are free as normal for use. The 2 floors shown are actually ‘clipped’ in place.
I used 3d Builder (the generic windows 10 one, I know…) for a crop for the ports & mash as required. I’ll have to look into a proper mesh software at some point.
I have used ACad & blender in the past, but it was few years ago so I’d have to brush off all the cobwebs and relearn the systems again.
I’d post the file, but it would run foul of the copy right requirements of Printable scenery.