I got the solution ( tested and working)
The Xposed framework
How it works? it simply mod 2 files in framework ( absolutely safe and you will not loose an mod) giving it the possibility to run the app that can lock every app in memory ( the app can also change apps DPI etc but this in an other story)
1) Download and install XposedInstaller_2.1.4.apk
2) Launch the Xposed Installer and click on "Install/Update"
4) install the file XposedAppSettings02_1359680060_4464.apk
5) Reopen the installer Xposed the Modules tab and enable Xposed settings app
6) Open xposed app settings and start to set
The option to set the "lock in memory" is "resident" ( just tick it and press the diskette icon to save ! )
here an example
the idea come from leonardoaraujo's post about per-app DPI but i noticed that them was older version and the persistent in memory was not working
so i investigated a bit and BANG, the solution
I'm not responsable if something goes wrong, higly suggest a backup!
WORKING on 4.2.2
All credits to VillainTeam that done both apps