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You can use whatever you like, but above 120mm, maybe 150mm, the "image slit" drops off very very rapidly. That's to say, tilt the lens a little and POP the image rapidly darkens at the edges, top and bottom, resembling a blown, old-school TV tube.
It's not what I'd typify as a "cool" effect, it's rather just kind of limiting and useless. But, that's why dedicated TS lenses that I know of, die off around 90mm or so.
The vignetting or shadowing happens to all focal lengths but yes, sooner at longer focal lengths. I find that about 8 degrees of tilt is about the max you can expect before vignetting with any M645 lens but that's in the vertical plane. It seems you can often tilt more horizontally before the vignetting. It also depends on where you've focused, close to MFD or infinity. Im not sure if this is because of the design of the adapter or simply shadowing from the cameras mirror box itself. I've never really worried about it too much but you do need to keep an eye on it. Some times it can actually work FOR YOU, kind of like an ND grad on the sky. Other times it blends into the shot and you don't even see it.
I started to make up a table with test shots for each lens at each aperture and angle of tilt but I was loosing the will to live. It's much easier to chimp. Chimping gets a bad rap. Remember when we pro's used to shoot 'roids' which was an expensive and slower way to chimp. That wasn't looked down on. And you got to charge for them too! But I digress...
I've used the 150/2.8 A on the Mirex with some tilt and it's fine, to a point.