I've been thinking, and I think the RC-2 might be used to continuously loop phrasings such as the slide riff on Dr. L'Ling that enters approx at 3:48 on the studio recording.

My reasoning for this is that he uses the two dl4s to play the two different drop d power chords, B and A, each sampled as single chords. So the intro is like B-A-B-B-B-B, being "one shotted" back and forth on the two dl4s (right-left-right-right-right-right). Then for the verses he will "one shot" B-B (right-right), and play the little riffs, thus still playing rhthym with Jake while playing his licks. So that leaves the slide riff to be recorded on RC-2. Of course, this is just my theory.

Such techniques can be seen here:
http://www.youtube.com/watch?v=SOIJjjpQj7c

00:27-00:37, the B-A-B-B-B-B intro loops.
00:37-, the verse B-B rhthyms.
03:42-04:36, the echoey slide riff.