While it will fit in the slingshot 200AW (horizontally across the whole bottom) it is a tight fit. So, I searched around for other options.
Here is what I ended up with:
Domke F-5XC
K20D with a Sigma 17-70 mounted, a Sigma 10-20 stuck into the half the bottom with the rocket blower behind it, and a Sigma 100-300 standing upright on the other half from bottom to top. The wired remote, extra battery, flash media case are stuffed into the little pockets (I wish they had a flap on them).
The lower flap is 3 inches tall and 9 inches wide at the bottom. The sides taper inwards so the width is 8 inches at the turn to horizontal on the zipper.