[cypher]

If one ham is more dominant it could prevent the other from getting around the cage easily or getting to food & water with that many tubes, if the more dominant one decides to attack the other it really would be difficult for the less dominant one to escape easily, other than that as I said before if they did fight getting to them & stopping it in time if they were in a tube would be difficult.
Ideally you want a set up where there is nothing & no area where one or the other may become territorial & try to prevent the other getting to something or using something or fighting over it.
It's generally accepted that you stand the best chance of success keeping a pair with a very simple basic layout, no levels , tubes or too many toys.
I keep trying to look back at your photos to try to explain what the problem is but they are so huge it makes it too difficult!
As for sand I think some reptile sand may be safe but some aren't so better safe than sorry & stick with chinchilla sand.