> But as I use only Windows and Linux, I have a lot of trouble in making a
1920x1920 Quicktime .MOV for those wanting it.

I forgot to comment on this....

There are very few people indeed for which a 1920x1920 fisheye would be
appropriate, namely those with a 4Kx2K projector and full frame fisheye lens
(very uncommon).

If someone has an SXGA+ projector and full frame fisheye lens then they only
need a 1050 square fisheye. If someone has a SXGA+ projector and 1/4 truncated
fisheye lens then they only need a 1400 square fisheye.

If someone has a HD projector and full frame fisheye lens then they only need a
1080 square fisheye. I'm not aware of truncated HD based systems but I imagine
they peak at 1600 square fisheyes.

A SXGA+ spherical mirror based system is limited to about 1200 square fisheyes,
1400 if you want to push it. An HD based spherical mirror system is limited to
about 1600 square fisheyes.

In summary, if I were producing fisheye content for single projector systems I
see little point going above 1600 pixels. Those with lower capability projectors
can save lower resolution versions themselves. For QuickTime I would choose
Photo JPEG on high quality, or for an end user (if it wasn't going to be
rescaled/saved) then h264.