Great thanks all. My reckoning on the Oban->Oban would be:
1. Friday night or very very early Saturday morning drive up to Oban
2. Saturday. Ferry to Barra. Do some riding round Barra (up to 50Km)
3. Sunday. Ferry to Eriskay. Up South Uist. Probably aim for somewhere north of Creagory (75Km)
4. Monday. Up to Berneray. Aiming for 2ishPm Ferry. 45Km. Then up to Luskentyreish. A further 25Km (70Km total)
5. Tuesday. 15Km in morning then Tarbert Ferry. 11.40am on a tuesday. In the afternoon aim for a further 50Km down Skye (65Km total)
6. Wednesday. Remainder of Skye 50Km to Armadale. Mid afternoon ferry. Get another 15Kmish done. End up somewhere around Inverailort. 65Km total.
7. Thursday. Aim to get to Kilchoan 65Km
8. Friday: Ferry to Tobermory. Would probably spend the last day mooching around Mull and stay over on Mull. Can do any distance really. Minimum is 35Km.
9. Saturday: Craignure ferry back to Oban. Drive home.
Could add an extra day onto that somewhere and come back on the Sunday. also have a day spare in the mix on that route as mainland-mull-mainland is do able in a day easily.