How batch change duration of stills in Media Composer?

Okay... since you're on a MAC, keyboard buttons may differ.

In script mode, select all the stills within the correct bin, with CTRL (Command I think for MACs) + A.

All should be highlighted.

Using the following numbered keys (not a numpad, but the numbers above the QWERTY section)...

1 = Back 10 frames
2 = Forward 10 frames
3 = Back 1 frame
4 = Forward 1 frame

With them all selected, clear the in/out points to start with. Pressing the usual 'G' key.

Move forward a few seconds (several presses of the '2' key). When done, press the 'I' key to set an in-point. Move forward three single frames by pressing the '4' key. Press the 'O' key to set an out-point.

The marked in-out duration for all your stills should now be 3 frames.

Any MAC users feel free to chime in here if the process is radically different.