Honestly Stevie I think the tannin should be about right! The red berry tea bags don't really contain much tannin. I've successfully used 20 of these along with 5 black tea bags in a 5L DJ and the tannin was pretty perfect.
Though if the tannin is to high I'll let you guys know on the taste test so you know to tone it down if anyone decides to do the recipe themselves.
Of course, this is entirely experimental and although I have used all these other ingredients in different recipes in the past, I wouldn't recommend anyone to try this until I finish the batch and give the verdict!
It could be awesome, it might be awful, you never really know until it's been racked!