[brickeyee]

You will need light and sky screens to diffuse it.
Your solution appears sufficient.
I use UV illuminated screens with mine.

UV or IR?

UV is a PITA to generate.

 

[brickeyee]

This will not work. I had to do the above because of the fluorescent lights in the shop were messing with the chronograph. You can't tell because they do it so quickly but fluorescent lights actually turn on and off and this will mess up chronograph readings. The light needs to be incandescent, Or might even give LED's a try if my first try above wasn't so easy and happened to work.

For just daytime use I might try a sheet of this and make one giant "sky screen".

http://www.homedepot.com/p/Suntuf-26-in-x-6-ft-White-Opal-Polycarbonate-Roof-Panel-159856/206395301

If you pick a cloudy day just set your chronograph out there, no need for the screens.

Even an electronic ballast fluorescent flickers.
It may be 20,000 per second (or even higher) but that is not going to work with a photo screen system.