Thanks
@JackMiles for your excellent ideas and summary. Yes we are not fans of 1 night stays. I had been looking at a suggested route on the WA tourism site, but it looks like the area is not as spread out as I first thought. Its good to get first hand advice from people on AFF.
Its nice to have a base and not to have to pack up and check out.
I will look more at distances between sites and towns. The Katanning stopover was only added to the trip back up to Perth, as I was not sure how long it would take and what the road would be like. Would you do the inland route up past Katanning and Williams?