Skew on both fade and release

Are you looking for something like this?

Yes, with the White part travelling from one side to the other, starting and ending in black. And being able to determine how wide it is..

Yes, with the White part travelling from one side to the other, starting and ending in black. And being able to determine how wide it is..

I think these setting adjustments are more in line with what you want?  Pulse Width and Shape are the settings to adjust shape and size.

That certainly got me a lot closer - Thanks a lot!  Now I just need a way to make it not loop. I've set loop to count 1 - but it still starts to reappear before the instance ends.. I just want it to appear in one end, parse across and end..

Try the burst effect instead of the wave. It was designed this kind of effect. It has a Absolute property in Pulse width that lets you set how many fixtures you want to run it on instead of having to play with percentages. And it doesn't loop if you have count set to 1

Hi - and thank you all for helping out.

I've tried the burst effect, but it has the same issue for me - it reappears in the start of my string of fixtures 

what I have done to workaround this is to create some "dummy" fixtures that are not part of your rig and place those at the beginning/end of your matrix/group. This helps with effects that tend to wrap around on start or end of the timeline.

I thought of that, but hoped for an easier way ;) 

I found that the burst effect doesn't reappear when you set the release to 0

Thanks for the inputs - I'll continue testing, trying, learning and designing 

Yes for a one shot burst set the fade time and release time to zero and the count to 1. The length then will determine the speed. 

Another method, not requiring dummy fixtures, is to create a pixel matrix of your fixtures. Then use a one color gradient with a fade time and wipe the gradient on (you may have to adjust the angle depending on your matrix). Add another gradient on a different Matrix line that is color black with a slight offset from the on color. If you want to allow for a gap, then make your pixel matrix bigger than the amount of fixtures you have.