Um, Sam, I use all sorts of lenses in barrel hung in front of a Copal #1 with no problems. But on 2x3, not 4x5. The shortest lens I use that way at infinity is around 120 mm.

But hanging a lens in front of a #1 with 4x5 is more problematic because of vignetting. Here's the test: if the distance from the lens' exit pupil to the shutter's diaphragm is less than 20% of the distance from the lens' exit pupil to the film plane, vignetting will not be a problem at infinity. This based on reasoning from similar triangles with the facts that the #1 shutter's maximum aperture is 30 mm and the diagonal of 4x5 film is 150 mm.

You want 1/500? You're dreaming. A cock-and-shoot Copal 1's top speed is 1/400. A Copal Press' top speed is 1/125. Larger shutters (Alphax, Betax, Gammax, #3) are all slower.

Since you want to carry only the Tachihara you can't use your Speed, mounted in front of the lens, as the shutter. That's the way to get high shutter speeds ...

Good luck, have fun,