Which cage?

[Sally]

This place has that 30x18x36 cage with a pull-out grate. I can't tell you if that would affect the stability if you joined two cages together, perhaps the vendor could tell you. These are a little more expensive, $144 includng shipping for a case of 2 cages, which works out to $72 per cage, but they do have the pull-out grate.

http://www.countryfeathers.net/breeder-cages.html

Years ago, I did join two of these cages (fixed grate) with zipties. Sitting on a counter, they were perfectly stable, but in summer, there was too much sun coming in the windows, so I needed to move the unit. My brother helped me, the cage unit was quite wobbly while we transferred it, but that is to be expected when carrying this unit from one place to another.

[Harley2013]

I just went thought this. For the past few days, originally I started ordering the F040, then read and decided that the finches would more than likely only use the top half of the cage, being up high, and seldom go lower. So I cancelled that F040, and found a double flight, ( not the color I would like, because it was out of stock) so settled for black. Double flights give them the horizontal flying space and more room for decor, and things.