Yes it's 7mm bar spacing although I believe some gaps at the edges (joins) could be nearer 1cm and the top door often can have a gap under when closed (I keep it closed tight with a peg on our skyline cage). The edges you could put some cable ties along if you're worried to pull them together a bit. I did that on a Savic cage.
It is quite a tall cage so a long drop from the roof to the bottom, and a ramp to land on on the way down (if your hamster decided to climb to roof level or monkey bar. So as CMB says - think about set up. I've seen some nice examples of dwarf set ups in an Alexander. A couple where the shelves were made into almost a full level (using the ramp as an additional joining shelf, covering the gap in the middle mostly and having a bendy bridge ramp up the side where the roof is lower). And also having the shelves low with substrate heaped up in the middle. Will add the links if I can find them.
Here's the second set up mentioned - it's the photo at the bottom of the article
https://mischiefhams.weebly.com/alex...ge-review.html
Sadly with the demise of photobucket, the other images don't show on google any more. But if you can imagine the standard set up with the shelves half way up the bars, you have the two end shelves, then the middle joining shelf, then use the ramp along the front as another joining shelf, rather than as a ramp. That gives you virtually a full level apart from a smaller hole in the middle. A piece of wood laid across most of the hole covers that, and a long bendy bridge ladder goes up into the remaining smaller gap. You could then hang something from the roof over the gap where the ladder goes up so it can't be fallen down. Wheel and/or flying saucer on bottom level on the substrate.