I am currently in the process of writing a song called Superbia (Pride) with my band, and just as I thought I was done I decided to swap a part of downpicking to a sweep picking run instead.
This, however, turned out to be quite troublesome.

You see, it was originaly four beats, two sevens on the D string followed by two sevens on the E string, but when I switched the four notes to six sweep picked ones I realized it's pretty hard to get the finger positioning in correctly (I just sweep sevens straight down, starting on the E strings). Put simply, my fingers won't fit and they make the notes come out REALLY sloppy.

Any suggestions on how to fix this? I tried sweeping in a decending order, starting on a seven, followed by and eight and a nine, but it just doesn't sound right.
Don't sweep all on the same fret. Or if your really set on it, find the note on another string so it doesn't get all sloppy sounding, it will make it more of a run though, not a traditional sweep.