Yeah I really would be cautious, I just did the reverse (Flynn -> dokku), and found that even after re-deploying a few images on Flynn it wasn't cleaning up images and disk space was disappearing fast (was hitting my 20GB linode limit without having half of my apps deployed).
So I ended up giving dokku a shot and that thing is lean in comparison, I was able to setup all my apps (about 7 of them) including redeploying some of them many times to get them working, and they only ended up totally around ~10GB on my server. Which left plenty of room for me to also host my music library (~6GB) there too with my music player[1].