Partition size changed after install SlimLP but not with ParanoidLP

Hi, I'm new in XDA but I have been reading a while, Thanks to all developers and testers

I have an skyrocket and I trying to use a lollypop ROM. While I was reading about it I found how to change the partitions of my skyrocket to have a system partition from 568mb to 1.2gb. So I did it.

1.- Start the skyrocket in Download mode
2.- Using Odin 1.85 re-partition with the PIT file from here http://forum.xda-developers.com/galaxy-s2-tmobile/development/mod-partition-internal-memory-t-989-t3051556
3.- Reboot the phone to recovery
4.- Reformat all partitions. Wipe -> Advence wipe -> Select a partition (cache/data/system/interal) -> repair or change file system (here show the old size) -> change filesystem -> select the filesystem (ext4/f2fs/fat)
5.- Install Paranoid android with tk_gapps-stock, 799mb both files.
6.- All work excelent :D

Now I'm trying to test slimlp-5.1-beta-0.6-official but I realized that after installed it the system partition changed from 1.2gb to 568mb, something that with paranoid does not happen. :confused:

Why happen this? Could be the installer? If is it then please I ask to the developers of Slim to fixed it please