Modern ignition systems can light off VERY rich charges, but if you get TOO silly you can still get bore washing.

I've seen AFR maps in some rally cars over here that had them set at 10.8 and even richer, so I'm not too concerned about anything at 12.7

You can't use the words 'fuel economy' and 'max power' in the same sentence anyway, so it is a moot point.

I set my stuff up for about 14.6 at 'cruising' speeds and loads (low TPS and MAP) and then go richer at full chat.