Housebuilder extension change standard board sizes

I have an imperial HB installed.
http://sketchucation.com/forums/viewtopic.php?f=79&t=56772#p519210

Reason why I deinstalled metric is that it have mistakes in sizes.

I need to be able to change the space between the studs, I need metric 580mm which is 22.8346 inches, not 24
I also need to change board sizes, it has only 2by4 2by6 2by8
and I need a board of 1.9685by5.90551, very close to 2by6 its a metric board od 50x150

initial 2by6 cut from wood is exatly the same size, but after it is dryed ant cut in becomes 1.49by5.5 which is 140x38 metric (its actual size in housebuilder). But the board i will use is 150x50, so diffrence in metric is very big for me