Golden light extract HELP!!!!

So I have a buddy that wants’ to use dark malt extract and I only carry
Golden light, amber and Wheat DME, right now. He has a recipe that calls for dark DME. He "is" using steeping grains. What should I add to the grain bill to add to the "Dark" that he will be missing from the Golden light DME that I carry?
HELP!!!
Cheers
Jay

What kind of beer is he making?

It's a porter of sorts

Style: Robust Porter

TYPE: Extract

Taste: (37.0)



Recipe Specifications

--------------------------

Batch Size: 5.00 gal

Boil Size: 2.50 gal

Estimated OG: 1.062 SG

Estimated Color: 31.5 SRM

Estimated IBU: 32.9 IBU

Brewhouse Efficiency: - %

Boil Time: 60 Minutes



Ingredients:

------------

Amount Item Type % or IBU

5.00 lb Dark Dry Extract (17.5 SRM) Dry Extract 58.82 %

1.00 lb Caramel/Crystal Malt - 10L (10.0 SRM) Grain 11.76 %

0.25 lb Black (Patent) Malt (500.0 SRM) Grain 2.94 %

0.25 lb Roasted Barley (300.0 SRM) Grain 2.94 %

1.75 oz Northern Brewer [10.40 %] (60 min) Hops 32.5 IBU

0.25 oz Northern Brewer [10.40 %] (2 min) Hops 0.4 IBU

1.00 oz Licorice (Boil 60.0 min) Misc

8.00 gm Gypsum (Calcium Sulfate) (Boil 60.0 min) Misc

1.00 lb Brown Sugar, Dark (50.0 SRM) Sugar 11.76 %

1.00 lb Molasses (80.0 SRM) Sugar 11.76 %

1 Pkgs English Ale (White Labs #WLP002) Yeast-Ale





Mash Schedule: None

The recipe already has roast, black patent, and caramel malt in there. The only thing I can think of is that the total of 0.5 lb of roasted malt isn't enough. I'd add some chocolate malt, maybe 0.5 lb.

So maybe .50 of roast and .50 of Choco. leave the Black malt @ .25#? Sounds good to me.