Tamarind Dunkelweizen-How much Tamarind puree?

Can anyone with experience using this ingredient weigh in?

Here is the base recipe that I'm using:

4.25 lb Munich Malt - 10L (10.0 SRM) Grain 47.50 %
4.25 lb Wheat Malt, Dark (9.0 SRM) Grain 47.50 %
0.25 lb Carafa II (412.0 SRM) Grain 2.50 %
0.25 lb Caramunich Malt (56.0 SRM) Grain 2.50 %
.5 oz Saaz [4.00 %] (60 min) Hops 7.0 IBU
1 Pkgs Hefeweizen Ale (White Labs #WLP300) [Starter 2000 ml]
Yeast-Wheat

My questions are:

1. How much tamarind puree should I use for an upfront and dominant flavor? I am thinking between 12 and 16 oz.
2. When should I add it? Flameout or secondary?