I've been using the python barrel kit for a while now, and I'm not so sure anymore if it does anything for open-bolt markers... It definitely works well with my Cocker because it prevents roll outs.
Some people on MCB have argued that the python kit is too short to make a difference on open-bolt markers, and that the control bore needs to be 6-8"... I don't know what to think anymore.
But, if you use the stock barrel with the python kit, it wouldn't hurt to polish the bore of the stock barrel with mother's mag or something similar.
Also, it seems like a lot of the tourney players have barrel kits, but over-bore by quite a bit to be able to shoot any paint and avoid breaking paint in the barrel. What's the point of having a kit if you're only going to use the .696" bore/insert?