Shuttle in daylight?

[Tantalus]

With the Shuttle launch now delayed 'til Monday (at the earliest), it's first pass over the UK will be in daylight. I know the ISS can be seen in daylight, so I was wondering if it might also still be be possible to see the Shuttle with the aid of a scope (120mm f/8.3 refractor).

If it launches at 19:34 BST, then it should pass my location around 19:54. At that time, the Sun will still be 4 degrees above the horizon, and the Shuttle's magnitude will range from mag 4.8 to mag -1.0 at it's brightest (Alt 22 degrees).

Of course, to stand any chance of seeing it I'd need accurate tracking details; but assuming I've got the scope pointing in exactly the right place, am I going to catch the Shuttle? Is mag -1.0 worth taking a chance on or would I be wasting my time? Any thoughts on what would be the limiting magnitude?