For comics I use a 3784 pixel width with a height around 6000 or 7000 pixels. For the Chrysalis picture in the tutorial I worked in 2539x1929 pixels. And the Fluffle Chrysalis picture was 3563x3452 (a bit on the large size). At the end I re-size down about 33-60% from the original.



You might need to take system memory into account too. For the last comic I was at 95-98% memory use so I couldn't make it much larger.