We've umm'd and ahh'd for a couple of days over this 6th test roast.  In the end we think it is too tangy so we ran a 7th test roast tonight & found ourselves in need of some inner warmth just now so we're into it already and of course its too early to be sure but it tastes very close to the mark.  The tanginess in coffee is always more noticeable first thing in the morning than in the evening.  In the evening we find the tanginess easy to live with, but in the morning we find it becomes a bit irritating as you work you way towards the bottom of the cup.  The signs are good that this 7th test roast has just bought the scales to balancing point in terms finding a happy medium that is pleasant throughout the day.  More soon as this 7th roast evens out over the next few days.