faking a long transition between stills - iMovie 09

Making a slideshow - I understand you can't have a transition longer than the still photos on either side of it. Is there a way to obtain a long fade-in (say 10 seconds) from white at the beginning of the slideshow, where the first photo starts appearing immediately?

I can have this:
blank white screen (5 secs) --> cross-fade transition (4 secs) --> first real picture (5 seconds),

but this results in 5 seconds where nothing happens, a 4-second fade-in to the first image, then that first image remains on-screen for 5 more seconds.

What I would like is something like this:
blank white screen (0.5 sec) --> long cross-fade (takes 10 seconds for image to appear at full darkness) --> first real picture (stays for 1 second longer, after the cross-fade is completed).

I know iMovie won't let me do it that way if I try to proceed normally. But does anyone know of a way to "fake" this sequence of events? It doesn't sound complicated enough to be impossible...

Well, that's exactly what I've done, but it still gives me the problem of durations: either I have to sit and stare at a completely white screen for a long time before the transition starts, or if I make the duration of the initial white screen short enough then the transition is forced to happen too quickly.

I'm trying to have a short duration on the empty white screen before the fade-in starts, a long fade-in, then a short duration on the completely faded-in first image.

Good idea - but it doesn't solve the waiting before and after the transition. You can have this:

White screen (5 secs) --> cross-fade (5 secs) --> 50% image (10 seconds total including the transitions) --> cross-fade (5 secs) --> 100% image (10 seconds) --> transition to second image etc.

There are 5 secs of nothing at the beginning before the first transition starts, and 5 secs of the fully visible first image before the next transition.

Does anyone understand why iMovie imposes this apparently arbitrary rule about transitions not lasting longer than half the duration of the stills around it?