Disclaimer - my post is related only to original subject of this thread, LegacyXperia CM13 build,..... .
Yeah. I have an Xperia Pro (MK16) and as I wrote before, long time ago: the best we can have on Xperia 2011 devices is CM11, Android KK. That is my personal experience, with lots of tuning and so.
With CM11 device is not that fast with current apps, but it does work. My Xperia Pro, root enable, Xposed installed, is running fine as backup device.
To let it better I do suggest to:
- delete all system apps that you don't use
- move Google Play Services to internal memory (as user app.... Yes! It does work and help a lot to free system room besides internal memory on updates)
- now that have some free system memory, move highly used user apps that is not frequently updated to system (xposed + modules for instance, browser,.... )
- have the fastest SD card you can and partition it to use Link2sd or Apps2sd
- set Link2sd / Apps2sd to link (move) everything from user apps to ext partition on SD card
- prefer light/lite apps, like Naked Browser Pro, Hermit (for web apps instead real apps), Facebook Lite, Messenger Lite,..... (even better without Facebook if possible)
I haven't tried yet, but I think it will be even better if run CM11 without Gapps. No Google Apps at all. Then sideload all apks, use apkmirror, yalp Store, F-DROID to install apps.
An alternative, medium term solution, can be to try Mkcrog with CM11. But I'm not sure if works, I haven't tried that also.