Sorry, but since this was not posted in Cosplay (where it SHOULD have been posted), it was not noticed until now.
Nothing has officially ever been stated in the rules on this issue because until now no one has asked about it.
Are you sure you can handle preparing for two skits? That's a LOT to ask a single person. I wouldn't recommend it - you have to learn two parts, and if you are unable to make it to Kumoricon for some reason you will have two skits that are missing a person (which may result in two skits dropping out of Cosplay, which is a BAD thing).
Here's the skinny:
(1) You may participate in up to two skits, however your name can only be listed as a participant for one skit.
(2) Only the people whose names are listed as participants in a skit will receive prizes / plaques if the skit wins
(3) You may WRITE the script for only one skit, and you must be listed as a participant for the skit for which you wrote the script