From: PDX (and now) London, UK
Because you can differentiate tasks for a FP unit, such as flying both search and ASW, there is no need to have the two units on the AV. Just keep the larger one that fits on there and use the other from a land base.
If you do want to downscale units, which I do from time to time, just hit the resize until it lets you change the number, wait one turn, and if in a base hex it should downsize the group. if the extra planes overfill the group it may take a day before the remove arrow appears to take them out, or just 'upgrade' to another plane type and change back to what you want the next day.
"Success is the ability to go from one failure to another with no loss of enthusiasm." - Winston Churchill