Sorry, I never did see your question.
If I recall this is how it goes:
$ sudo bash
$ cd /userdata
$ fallocate -l 64000000 SWAP.img
$ mkswap SWAP.img
$ swapon SWAP.img
That will increase the swap to 64mb, as a note the '-l' is a lower case L.
I found the N5 unstable until I had 128mb'ish. However the primary app I use is Morph and that has been improved since the last I tried UT on my N5. Depending on how much you care to risk you device's storage you can go as much as you want. I used it for 2 months as a daily driver with 512mb of swap and it is still running fine (but as an Android device atm).