or.....
in the Yamaha - pan all drums hard left and record on either track 1, 3, 5, or 7 of the mr8 (end up with 1 mono track of all drums - mae sure you get the levels right)
and pan the guitar hard right, or plug into input B of the mr8 and record guitar on track 2, 4, 6, or 8
at least then...