A strongly fed bp will likely not ball up much, as it is probably uncomfortable to do so.
I do not know about the movements of your snake as I cannot personally see it. I expect it is just very full and trying to digest all the feedings. Keep your hot spot up around 92-94F to aid in digestion. Digestion consumes a lot of energy and the snakes metabolism will all be used for digestion instead of activity. Keep water bowl full and change often.
I would switch to rats if possible... "shake and bake" a rat in some mouse bedding to help switch your snake to rats.
I have had a few very well fed bps that act similar, and look the same. I have a 2013 1.0 Enchi Albino that I picked up in Daytona at 120g, and fed well in order to breed this season. His proportion was similar to your snakes..... thin head and neck while his body was growing quickly. He is now more well proportioned after a few months. First picture is probably somewhere around 300g. Second pic is just a few weeks ago over when 500+g and just introduced to a big Albino girl- more proportioned than when gaining weight rapidly.
http://i254.photobucket.com/albums/h...ps26435c11.jpg
http://i254.photobucket.com/albums/h...ps4e44c8f7.jpg