where do you need some light?
as you have 2 links in the etherchannel you need 2 separate VLAN's for each of the "p2p" links.
the rest is easy:
on SW1: put one link into access-vlan X, the other one into access-vlan Y then build a q-in-q tunnel to SW2, there the same to SW1.
just be sure to tunnel also the pagp protocol (l2protocol-tunnel point-to-point pagp).
-steven