Just wonder if it will fit into the field of view?
With the 31AF03, the solar disc will fit in a square of around 760x760 pixels (including medium sized prominences), and the 31AF03 has a pixel size of 4.65um.
With a 21AF04, the pixel size is 5.6um and thus the pixel will accomodate slightly more field.
By simple calculation, the 21AF04 will be able to fit horizontally, but not vertically with my existing instrument. Therefore, I would rather stay with my 31AF03.