4 issues should be fine. All the way through my (BPP) training course we were being advised to aim to do 4, with perhaps a brief mention of "other issues" if you get chance. If you look at some of the posts in the T4 forums (in particular one which asks what prioritisation people who passed the last sitting had) you will see most people went for 4.
I did 5 and got 35 credits, frankly if I had missed out one of the less important ones then I would probably only have been down 3-4 credits at most, which would still have been a comfortable pass. One or two people said they passed with only 3 issues.
