Without thinking too much about the daily distances, timing, or cost (

perhaps that's why you said and not get on the boat?) you might make this work:
VII to McCargoe. Day hike around Chickenbone
McCargoe -> Todd -> Hatchet -> Malone
VII from Malone -> Windigo
Windigo -> Island Mine -> Windigo (overnight or in a day?)
VII or Sea Hunter home
It doesn't eliminate any backtracking, but remember it's always a different trail going the other way

. And in this case, the backtrack is downhill

.
Or just go home from Malone and save the Greenstone for another trip. We know this won't be your last!
25: MB | 24: MB | 22: BI | 21: RH-DF | 18: MC-DF | 17: WI-SB-WC | 16: RH-CI-RH | 14: BI-MB | 13: RH | 12: MC-TH | 11: WC-HC-WC | 09: MC-RH | 05: MI-MB-RH | 02: MC-CH | 01: BI-RH | 79: RH