I'm kinda digging up an old thread but I thought I'd give everyone some insight because this thread gets a lot of views.
my balers do take two windrows just fine - however for my first crop I had to go very slow (A1) on my tractor. That's about 1mph. My second and third crops were just fine, I did have the hairpin on one of the knotters fall off but other than that the baler worked fine. I just had to make sure (mainly on the first crop) that I wasn't going too fast on some of the spots so I wouldn't plug it.
I have an old NH 57 rake that I've been using and it was great - just had to adjust the 3 point hitch so it was parallel to the ground and didn't pick up rocks/dirt. I also decided that when working with small balers, I'm better off using a small rake to combine windrows instead of using a v-rake so I don't have to drive on top of my hay and shatter more leaves.
If you're raking alfalfa, make sure to rake it earlier on when you have at least 45% moisture so you don't shatter the leaves off. Also, raking early in the morning or at night time when you have dew reduces shattering as well.