I agree with Tom -find the profile that works best for you, rounding the corners on a bigger slick will certainly make it easier to slice with... you probably have a chisel with nice square corners to clean into the corners of the joints with anyway?
I have a 2" japanese slick which is kept square and a 3" western slick which is kept rounded......
When you say there is a rib down the center, that makes me think you have an old framing chisel...is it heavy?
