Minimal root package from WiKi is a bit outdated - package was not updated for a while. I may be wrong but one of the reasons is that porkupan switched to my minimal root some time ago
App2SD is compatible with any root package (as long as it has latest Sony firmware version as a base - Linux kernel version is important).
The only reason I am suggesting to install root BEFORE App2SD - App2SD needs around 500KB of free space on /system and my minimal root surely provides more than that. You could only have all benefits of App2SD if you are using it with my latest minimal root (or any root which incorporates packages from latest root) - due to the bug in Android services framework which is fixed there (I guees you already seen our exchange with uboot on this subject).
So the easiest way to go would be:
1. Make sure you have clean Sony firmware of the proper version
2. Install AMR
3. Install App2SD
4. install applications
5. Enjoy
Hope this helps