generally speaking, shooting the film at a slower asa will give you more shadow detail but minimal effect in development. Altering the development alters the contrast, and by the sounds of it, your 1st roll was contrasty enough although you recognised the light would have been contrasty. If other rolls are also in contrasty light, I'd be inclined to decease developemt a bit (10-15%) and see if that is better, then fine tune some more if required (of course you could hold off developing these rolls and do some tests 1st) I've never heard of increasing development for MF films, but if it's in that book, they would have some basis for it (Steve's on this forum, so email him for an answer from the horses mouth!).
You should get some nore knowledgable replies