We are just doing the Edexcel Autumn 2016 Mock set 1. Now that the papers are designed to have 50% of their content at grades 7-9, rather than the old spec which had 25% of marks at grades A-A*, might it not be reasonable to suggest that the marks needed for grade 7 would be a little under 50%? Why? Well on the old spec the mark needed for grade A was about 70% (compared with the 75% of marks available for questions below grade A.) So working with this figure and assuming candidates this year will be similar to those in previous years, we should not expect to have to get any grade 7-9 marks to achieve grade 7. That means I'd start looking for the grade 7 boundary around 47%.