[Hampshire] Changing font sizes used by Tcl/Tk applications

Can anyone point me in the right direction on how to change the font
sizes used by Tcl/Tk applications? Specifically I'm trying to use the
"stopwatch" application (in Ubuntu) and it's being rendered with a tiny
font. I'd like to tweak the font sizes to make it legible.

I'd also like the numbers to appear really large, so I can fill the
screen with it and it still be legible from a distance. This I suspect
is not what the authors had in mind, but adjusting the font size seems
one way to do it. Another is to use an accessibility / magnifying
program of some sort.

Additionally, if one wants to set the default font DPI for X to 75dpi,
what should one edit and how? Google tells me it should be an Xresource
but I haven't found more than that yet.

Thanks,

Tony