Actually there was a tool called MonEd that could be used to tune existing monitors (DblPAL etc) in detail... However I never could figure out how to use the tool to get wanted results, except experimenting.
I could get the borders smaller with friend's 15" Microvitec, and also allow more overscan... and even cure disappearing mouse pointer (far right) with DblPAL overscan.
PS. Don't even ask how I did that, it was some 9-10 years ago.