Yerba Mate Stout creation help.

As a lover of stout and an adept of adding regional character to beer, I toughth of making a Yerba Mate Stout.
Yerba Mate is a great tasting, very strong, bitter, tanninic and caffeinated herb largely consumed on south america, I plan on adding a yet unknown volume of cold infused roasted Mate to the secondary and maybe a hint more on bottling day if needed.
It does have a lot of potential, my only concern is how to balance the added bitterness and if the high amount of tannins could spoil the beer.

Should I reduce my hops as to keep the bitterness down?

The recipe I plan on adding it to is this one:

Batch size: 6.6 gal

Pale Malt 8.5 pounds
Unmalted Barley 2
Unmalted Roasted Barley 1.3
Cara Malt 0.7
Weat malt 0.4
Coffe Malt 0.27
Goldings (45 min) 1.9 oz

I would love to hear the more experienced brewer's insight. Have anybody tried brewing with mate yet?

Edit: After some preliminary tasting I've decided to add arround 2.38 oz of roasted yerba mate to the 6.6 gal batch, it does bring a subtle tasty flavour.
But also, due to the mate's alcalinity all of the stout sourness was gone and a mild unpleasant leathery and soapy flavours were present... Should I acidify the infusion before adding it? Will those flavours wash off after fermentation?

Just brewed it yesterday. OG was a tad lower than what I aimed for, but I'm sure it'll turn out alright. As soon as the yeast settles down I'll add the mate and post the findings.

How are you adding the Yerba? Are you just adding the leaves or are you actually steeping them first? Im looking into a yerba beer for a friend of mine that drinks it daily. We just cant get Mateveza here in Jersey, so we are going to try and make it.

I let the leaves sit on an airtight glass container with water at room temperature for 3 days than I use a sanitized coffee strainer to separate the tea from the leaves, then add the liquid to secondary. I use ROASTED Mate, which, in my opinion, its far friendlier to beer (namely stouts) at a rate of 0.33 to 0.47 oz/gal. If you are using raw mate you might want to use a little less of it.

There are a few things to watch for when using Mate:
- Mate might add a lot of tannins to your beer, and even make it taste like cloth. Only use good, freshly roasted mate (which I believe must be hard to get out of south america)
- Do not, I repeat, do not let your mate get in contact with water above 180F, it will taste like satan's ass, seriously.
- I found that adding the leaves directly to the fermenter extract more tannins than I normally want to.
- Its darn tasty if you do it right