British strong/old ale recipe

[Erik the Anglophile]

So, I've made some invert #2 based on light muscovado sugar, and had an idea to use it in a strong ale style beer in the near future, I think the fudgy character of the invert will be really nice in an ale of that kind.
I wanted to use first gold, but my LHBS didn't have any in stock, so I decided to use EKG and a dash of Mandarina Bavaria, since I want a little fruity/citrusy flavor but not in your face IPA like fruity.

Grain Bill:
Maris Otter 2.11kg 64%
Munich 1 490g 15%
160g Rolled Oats 5%
130g Brown Malt 4%
130g Carabohemian 4%
260g Muscovado #2 8%

Hops:
Challenger 13.4 g 60 min
EKG 15g 15 min
Mandarina Bavaria 7g 15 min

Mash at 67c/75min and add the syrup with the first runnings when I collect the wort
ferment at 19-20c with WLP007 dry english ale.

OG 1.075
FG 1.014
IBU 37
ABV 8.1%

Beersmith estimates the FG to1.014 with 80% atennuation but I have a feeling it will be a little lower in reality, I aim for around 7.5% abv, is it likely I will have lower attenuation than BS estimate or should I aim for a slightly lower OG?
Thankful for any critique since it will be my first try at a beer of this kind.
Edit: it's a 10L batch (11L post boil) and the amount of hops at 15 min are meant as 2g/L flavor additions.

 

[Erik the Anglophile]

Anybody got any opinions? Also it occured to me that maybe I should mash at 68-69c for 60 min instead to avoid having the beer coming out too dry as it has a fair bit of sugar in it.

 

[Franktalk]

The recipe looks good! What yeast are you using? That might shed a little light on your attenuation.

 

[Erik the Anglophile]

The recipe looks good! What yeast are you using? That might shed a little light on your attenuation.

Wlp007 dry english

 

[Franktalk]

Then, yes, you may want to mash high. Not that a high mash temp assures low attenuation. Your best bet may be to forgo the invert and make up the O.G. points with extra dark crystal malt.

 

[Erik the Anglophile]

Then, yes, you may want to mash high. Not that a high mash temp assures low attenuation. Your best bet may be to forgo the invert and make up the O.G. points with extra dark crystal malt.

I don't really want low attenuation per se, just prefferably not over ~80%, wich on the other hand is the max capablility of this yeast, I'll mash at 68c and see if I end up in the high 70's - 80 somewhere.

 

[Franktalk]

That sounds like a plan.