The largest ive had upstairs was a 55g tank, but i have seen as large as 200gs.

I normally say keep aquariums on load bearing walls, preferably outer walls. With that said a 29g or 8g aquarium I do not think id be super concerned about it. As far as water changes you could always plumb in a RO/DI upstairs under a sink or haul the water up. That is up to you.