Wow. Word replacement run amuck. Try again, and anybody with a delete button, feel free.
Let’s see, .5mm translates to about .02” in real numbers — quite a lot. I’d say you could flatten now and no matter what the weather did you would profit.
Start coarse with the grit. You have a couple hours work ahead of you.
It’s quite possible to shoot with with anything from a 4 to a 7 on a shooting board.
The main advantage of the Longer plane is the sole in front of the cutter. Longer planes have more of it, so it’s easier to stay registered to the work on the back stroke. But keep in mind the Veritas shooting plane is only about 16” long, midway between a 5 and a 6. The Stanley 51 was an inch shorter – not much bigger than a 5.
Shooting with a 6 or 5 works fine. Smaller work is less work with the smaller plane.
If I ever come across a #7 that is damaged in the rear of the plane, I’ll cut it off. Maybe stick a handle up the side…