How to add extra hover-over area to link?

I’d like to display tooltip when user moves cursor near to link.
To hover over any link, user has to move cursor on the exact vertical center position of the link.
As link and border lines are thin, user need to put extra effort to place the mouse pointer on the exact position.
Is there any way, that we can increase this hover-over area of link?
Code samples would be grateful.

A typical Link template will look like this:

    . . .,  // various Link properties and bindings
    $(go.Shape, . . .),  // the main element, which is the Link.path
    . . . // arrowheads or labels or whatever

But you can have multiple link path Shapes in a Link, as long as you mark them all with isPanelMain: true:

    . . .,  // various Link properties and bindings
    $(go.Shape,  // a wide transparent Shape following the link path
        isPanelMain: true,  // on both this Shape and your original Shape
        stroke: "transparent",  // don't draw anything
        strokeWidth: 8  // something suitably wide to make it easy
                                 // to pick with mouse or finger
    $(go.Shape, { isPanelMain: true }, . . .),  // your original Link.path
    . . . // arrowheads or labels or whatever

A bunch of samples do this, including the FlowChart sample, but maybe we should talk about it in the Introduction page about links.