That's a neat idea....
As part of a set up rewrite, I had recommended a set of rudimentary test patterns.
They were designed to be 720x480 pixels which is THE standard for ALL graphics screens and the Broadcom video scaler chip converts that up and down to 480i, 480p, 720p & 1080i.
Thus the suggested OVERSCAN slide would always be accurate and we asked for gray scale and colour bars as well.
This was all part of the fact that overscan might be a real problem for the 207/317 new guide on old/small CRT's that are often mal-adjusted since the new graphics are designed to observe NTSC safe zones and unlike the current DSR5XX IPG's whose menu bars roll off the screen edge, the new ones have defined edges.
The overscan slide is also supposed to be used as part of a real-time screen position adjuster since the existing one has never worked and is too clumsy to use had it worked anyways.