Actually, kicking more is likely to just deepen the imprint of the inefficient kick you already have. You need to do something to replace the neural program
that causes you to spread your legs with one that will "instruct" your legs to remain streamlined -- i.e. to "draft behind" your torso.
I suggest you check out my response on the thread, answering Ed Levin's very similar question about his outsweeping right arm
The likely cause for your leg splay is very likely similar. You have some kind of lateral instability in your stroke. Your legs splay to act as outriggers to try to correct that instability. Tying your legs together will cause you to feel awkward and probably to "strongarm" the water with your pull, but I can't see how it will help you identify and fix the cause of your lateral instability. However Lessons 1 through 5 on the Easy Freestyle DVD
all include elements that improve lateral stability.