Alright, I did a very cumbersome experiment on the accounts table, because it's got a lot of columns of different types and not so many rows that it would take long to copy data.

Original size: 2498 MB. Size when columns are re-ordered: 2443 MB. So that's like 2.2% savings (55MB).

Of course, every table is different. Maybe you could squeeze more out of the statuses table, which is so much larger. But I'm not sure it's worth the effort...