Just thinking about laser building here and this thought came up. Is there any reason that you could not mount a tube vertically? It would give you more room to build your table. As a side note to this, I would suspect it would help in keeping the air pocket out of the tube. The first mirror would also have to be flipped 90 degrees also.
Ask a tube maker v this question, I gave only seen a tube used vertical once
Here is a vertical large format:
Thought about a 40-60 watt version like this?
I read somewhere that the bottom mirror in the tube gets dirty.
It is all about room and safety as in not damaging the tube that could be possibly exposed.
It be in a hard housing just vertical. i.e. an aluminum sqr tube .