6 days in Hokkaido with a car

In early November we will arrive in and leave from Sapporo where we plan to rent a car. We have 6 full days and would like to enjoy the island national parks. There is so much too see in Hokkaido and this website rates Shiretoku and Daisetzusan as the best. Are 6 days enough to visit both parks or is our plan too ambitous? Can anybody suggest a good route for 6 days?

The two parks can be visited in 6 days, but expect snow in the higher elevations of Daisetzusan NP. It will be too late for autumn leaves in central and eastern Hokkaido. Maybe not the best time of the year.

Southern Hokkaido, on the other hand, for example, Onuma Park, still seems to have some autumn colors:
http://www.rurubu.com/season/autumn/koyo/channel.asp?SozaiNo...