J.I.
If you haven't already, look at www.homeschoolreviews.com . You can get an idea of what worked and didn't work for different people.
Also, I've heard great things about Teaching Textbooks for math starting at the 5th grade level.
Look for a support group in your area. They often have lots of resources available to new homeschoolers to help with cirriculum choices. We belong to SAIL in McKinney and love it. It's a very active group.
And, yes, you are right... 6 hours of individual instruction is a lot. I'm not sure how much time 5th grade would take to hs, but my first grader averages about an hour a day of sit down work.