G'day BS,
don't over think the bye rounds, just try and keep an eye on your squad, and keep it reasonably balanced.
Mathematically, the best structure is: 8, 11, 11. This gives you 22 players in Rnd 11, then in Rnd 12 you trade 3 Rnd 12 players to Rnd 11 players, giving you 22 players in Rnd 12, then in Rnd 13 you trade 3 Rnd 13 players to Rnd 11/12 players, once again giving you 22 players in Rnd 13. It really isn't worth altering any structures to try and achieve this though.
A lot of Coaches try and avoid trading in Rnd 11. This is because any player you bring in will miss a game, so they feel it is wasteful. Those right at the pointy end of the table probably can't afford to take this approach, as it will put them a week behind their opponents in completing their team.
Another tactic I've seen adopted by a lot of successful Coaches is to Cash out their worst performing Keeper in the first bye week. Especially if it is a Round 11 Keeper. They then have a bank to facilitate good upgrades in this most important trading period. With a good bank you can make 3, possibly 4 upgrades in Rounds 12 and 13. Without a bank, you can probably make 2, or 3 if you are lucky. Trade agressively in Rounds 12 and 13, as it is the only opportunities to use 3 trades and bring in players you hope will not miss a game!