what the f (stop)?!

[480sparky69 69]

In a high contrast B&W situation, I would over expose but then cut back the developing time in the tank. .......

Also called 'pulling' the film.

 

[unpopular]

Expose for the shadows, develop for the highlights. So to get detail in the sky density, you'll need to process the film less.

If you're not processing the film yourself most pro labs can custom process at N-2. This should compensate for the +2 over exposure.

If you're processing the film, the exact timing for can be estimated with a generic characteristic curve, though this is pretty variable. Obviously you could read The Negative by Adams, buy a crusty densotometer from ebay, and do all the measurements yourself. But I don't think that's entirely necessary and with time you'll appreciate how your film and developer performs. Shooting large format you can develop by inspection, too - but I've never had the balls to try this.

Other than that, you could try reduction.