Could you pastebin me your JSON (cory@launchboxhq.com)? 2k of simple (`{"1": 1, "2": 2, ...}`) lines seems to work fine (slight delay) for us. Maybe your JSON is super complicated.
We can work on improving performance if we have 1k+ lines of super complicated JSON to mess with. :)
I personally tried it with http://www.json-generator.com/ ( I just changed the initial repeat to 50,70) - did not break, but a big lag after pasting for a few seconds