Thanks again guys for the exctensive and very useful input.
Jamawani - thanks for the mileage indicators and the various links. Super! So far I have planned from July Creek Campsite (Quinalt Lake) to Twin Harbors - which for me makes it a very long stretch (100km). And am contemplating to go either via BIAS 26 or a bit further down Kilpatrick Road to State Route 109 via Copalis beach, Ocean City and camp at Ocean City State Park (about 60Km/ 38 miles). And then the next day Ocean City State Park - Twin Harbors State Park (40 miles). This way I could indeed as you suggested detour to Westport and do the dune trail. From Twin State I either will go to the KOA or Bush State Park + stay for an extra day to do some birdwatching. From Bush State to cape dissapointment. Looks like my thoughts kinda followed yours even though I did not know that the other day when thinking about it

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Make sure to visit the Lewis & Clark Center at Cape Disappointment - then go for a swim in Deadman's Cove.
will do so.
KKtice - thanks your thoughts on Astoria bridge. I think I must have ridden it 25 years ago as well but do not really remember. So I think I will keep Astoria bridge in my plans. One does not get to cross such a long bridge every day.
John N - Good to hear that might I deviate to the Hood Canal I will not have any camping problems. Can I safely assume that one can camp in all State parks?