I mounted one of those inside my van, and took it out after just one trip. The thing was irritating! The annoying pitch and volume to me, was almost as bad as a fly buzzing round your head while trying to sleep. It it had moved a large volume of air, I might have tried to tolerate it, but I found it not very effective. Too small fan blade span means to move any air at all, they have to crank up the RPM. The Fantastic roof vent fans on the other hand, are pretty quiet on low and medium speeds, and the location is further from your ears.
At the very least, set up that fan and test it before going to the trouble of mounting it, to make sure you can live with it.
1995 E350 7.3 Diesel, 4x4 high roof camper, UJOR 4" lift