1. Crucial (obviously!) but often not known until they run in the race itself. An Eider winner might not stay the National trip.
2. Even more important. Other than the year of the two finishers, you just don't win Nationals unless you're handicapped to do so. The hard bit is working out in advance which horses are handicapped to win the race, often a matter of personal interpretation of the form.
3. Probably exaggerated in this race, ie the less suited you are the more it's going to affect you.
4. Not that important. Some winners are trying the race/track for the first time.
5. In my opinion, not that important. As I said earlier in the thread, I left out my top-rated Maori Venture, Rhyme N Reason and Royal Athlete because of jumping concerns. Haven't done it since. Paid off early with Last Suspect at 66/1.
6. Not that important. All horses are different in that respect. Some may have had to run a lot to get down to a favourable mark; others will have had a light season to protect a favourable mark.