How to maintain non-maxed out residences - Guide

I have seen many people asking for a way to stop upgrades to pop on residences (RZs) so we can have non-maxed buildings bringing variety and a nice look to our cities.

However we cannot know if EA will indeed implement this feature.

For this reason, I have used my secondary device, which has lots of Simoleons and Simcash (yes, it's a hacked APK that is useful for testing strategies) to find a out to have a few of each RZ.

The result I have aimed for was 3 RZs of each type, so 3 RZs for 52 population, 3 for 104, 3 for 154, 3 for 313, 3 for 752 and 3 maxed out for 1836 population.
This is a picture of the result:

http://oi61.tinypic.com/14smm3r.jpg

I will use 18 RZs for this method. It can be done for 24 but it is harder. I do not see how can this be achieve for more than 24 (i.e. 5 of each).  
About the upgrade bubble, I could not identify a logic with 100% of certainty, but it mostly seem to work like this:

Once you complete an upgrade, the game scans all RZs to find the next RZ that should get an upgrade bubble. If you have only a few non-maxed out RZs, the game will take longer to pop the next one.
If you have many of them, sometimes it will pop instantly. It also sees to look for some kind of chronological sequence. If you have Rzs A, B and C and you upgrade them in that order, it will first pop a new upgrade on A, then B and finally C.
This is not always correct but in most cases it is. Like I said, the logic is not 100% accurate.

Let's get down to business.

Step 1

You need to max out any other RZ that is not maxed out yet and make sure that you do not have any upgrade available. Wait for 1 hour to be sure that no upgrade will not.

These RZs need to be the last ones you will place in your city. You will not be able to upgrade any RZs above the initial upgrade afterwards.

Step 2

Place new RZs and upgrade to once (52 population). Do not upgrade them more than once. Place new ones as soon as they become available. Repeat until you have 15 initial RZs.

Step 3

Start upgrading them once more, to 104 population. Do not upgrade them past 104 population. Final result will be 15 RZs to 104.

Step 4

Upgrade 12 RZs to 154. Again, do not to beyond 154. After you are done, you will have 3 upgrade bubbles asking to upgrade to 154. Do not do this. let those RZs as they are. I will call them locked RZs, as you cannot do anything with them.

Step 5

Upgrade 9 RZs to 313. Bulldoze the 3 locked RZs stuck at 104. You will now have 3 locked RZs at 154. Good.

Step 6

Upgrade 6 RZs to 752. Bulldoze the 3 locked RZs at 154. You have now 3 locked RZs at 313. You are on the right track.

Step 7

Upgrade 3 Rzs to 1836, maxing them out. Bulldoze 3 locked 313 RZs. You should have 3 RZs locked at 752.

Step 8

Place 6 new RZs and upgrade them to 154. That means upgrade each one of those 6 thrice.

Step 9

Upgrade 3 of them of 313. Place 6 new RZs and upgrade each one once, to 52 population.

Step 10

Bulldoze the 3 RZs at 154 population that are asking for the 313 upgrade.

Step 11

Upgrade the 6 RZs with 52 population to 104.

Step 12

Upgrade 3 RZs with 104 population to 154.

Step 13

Place 3 new RZs and upgrade them to 52.

In short, what you need to do is upgrade until you have the maxed out ones and you need to lock the 752 buildings asking to go to 1836.
The only way to do this is by bulldozing the smaller buildings that are asking for upgrade.

The final count is 99 upgrades, so this is not an easy task, mainly as in my case, I want to do this for Tokyo RZs.

Try it out and let me know if you find out a better strategy!

I haven't triple-checked it, but I'll do it shortly and update this here.