Actually kris, I don't agree about the HQ at lev 20 at rear villages. Let us look at this in another way. Say you are facing a few thousand incomings at most of your villages. Forget all about safe villages, there are no safe villages. Yes they might be far from the front and will not be lost, but they are easy to put out of service.
An example: A player with 600 villages with 9714 p/village will have 386 more farmspace/villa for troops then someone who build to 10100p/villa. This would be all together 600*386= 231600 farmspace.
Now, 231600 divided with 20330 would give you ~11 villages of troops. Congratulations, now you can stack 2 more villages out of your 600, if they are all defvillages that is. That's just nothing. Like a fart in the space.
So with a few thousend incomings, both to the front and to your "safe" villages, you will probably move alot of troops to the front making your "safe" area exposed to nukes, while some or all of your frontvillages are somewhat stacked. What will happen? You lose your walls and your farm will be cated down in the rear and you can not rebuild troops or the wall untill your troops at the front get killed to under the amount of available farmspace, OR WHEN THE FARM IS REBUILT. Say you lose 2000 troops in the villa you are stacking and you are still not able to rebuild those untill the farm is back to lev 30. When this happen to a lot of your villages I wouldn't care much about those 11 extra villages of troops, they are not worth anything anymore, now you need speed when rebuilding. Not to forget, you can rebuild the wall faster as well.
I don't understand why people believe those few extra troops will make such of difference.
That's my two cents and as i'm really tired I might have overlooked something.