Yes, KISS, no mystery, it's the Cerveza Malto Seca recipe in brewing classic styles which I have made before but really never had the ability to control fermentation temps like I can now. It is a good recipe, and although I say 'a Guiness Clone' for me the Guiness clone is RiClarke's recipe on here using soured Guiness or not it's pretty close.
The few issues with Guiness cloning is the step mash to convert the flaked, carbonation, and alcohol levels... and for goodness sakes if you are trying to clone Guiness pick a product and stick w/it, they make a few and they taste different... The man himself had a 1.066+ brew to start so for those who say Guiness should be weak perhaps now it should be but it didn't used to be :-) or at least a stronger variety was available... If ya want to make the light session Guiness on nitro tap go for Ri's recipe on here, don't over do the grain bill and don't over carbonate... 1 to 1.5 vols ... Just sayin' ya want to clone ya gotta clone :-)
This recipe Cerveza De Malto Seca from Brewing Classic Styles is more coffee tasting than Guiness, especially if you follow directions and use a coffee grinder to grind the roasted barley up 'almost to dust'... it does produce an amazing flavor :-) So, just trying to get rid of the butter now (diacetyl) taste...
RiClarke's Guinuess Clone w/da sour 6.4% ABV 1057 SG 1009 FG