Double dipping is a good idea for kids that need the extra competition. If you're going to allow it at your tournaments you should make sure the sessions are 6-10-14 in the morning and 8-12 in the afternoon. Or vice versa. That would be a big help to the kids plus more kids would do it.
They did it at the Hutch Tournament. The problem with it is that it is sometimes hard for 8 year olds who aren't double dipping to wait until 1-3 in the afternoon to wrestle. My opinion is that it is best to keep the little kids in the morning/the bigger kids in the afternoon.