Did you try using ']' to cycle to larger fonts? I recently updated it with multiple font support and both a 24x24 and 32x32 font. The 32x32 I've tested on a Mac retina display with success, so be sure to try double tapping ']' to switch to it. It should result in a 3200x1792 area.
I can try to make it a bit more prominent in the description that this option exists. In a future update I'll see about auto-detecting an optimal font size instead of defaulting to 16x16.