In practice not unless you were planning 2 or 3 coaches only.
From testing I did a few years back only heavy modern diesels could manage 4% gradients. Go with 2% if you want most things to manage it will decent length trains.
2% means that you will climb 2 inches every 100 inches or eight feet will clear about a two inch climb.
So you'd need a 16 foot climb to get 4 inches off the baseboard.