Particle Problem: Speed control for bitmap style

I am trying to create a history timeline animation where images of human history fly in chronological order from the left of my screen to the right. I have a lot of images (100+), so I thought I use a particle animation for this.

I am almost there, but I have a problem with speed control.

Here's what I am doing:
Loader -> pEmitter-> pRender

The loader holds a sequence with my 100+ images.
The emitter is set to bitmap style with a Line region positioned off screen to the left of the images
In order for the emitter to use every single image I have, I am using a number of 1.0 in Controls.

I use a small velocity to move the images once spawned to the right.

So far so good. The problem is that the animation is WAY to fast and clumped, because one particle gets created every frame, and so the previous images do not have time to move out of the way.
I want one particle to be created every n frames (n between 5 and 10), and I want successive frames from my image clip on each particle bitmap.

If it turn down the Number of particles in the emitter control tab, for example to 0.25, then I see only every 4th image from my sequence, which is of course not what I want.

I thought I perhaps could use the Time Scale property in the particle style tab to counteract that behavior, but that does not seem to do anything, no matter what value I pick. Time Offset doesn't seem to be doing anything either. The documentation seems to indicate that it *should* work. What am I doing wrong?

Is there any way to get what I want? One particle emitted every few frames, and particle n takes the nth frame from my loader, and then moves on on its merry way driven by the particle animation?

Thanks!