Hi Mike
Sorry to hear about you adventures and pleased to hear crew and "Lya Maria" are now safe .
i have been looking through old stuff on the seal 22, but so far i have not been able to find any dimensions on the rudder blade..
the original was made of boiler plate but many people haver addapted and redesigned it.
you have the important bit which gives you the shape that fits into the rudder stock,
from the break you could perhaps cut the metal straight about 3 feet deep
My mate has a Seal Sinbad and i will contact him to send me photos and sizes but he is away for a few days and will get them to you as soon as
I hope this helps and will be in touch
Peter Lowry
Commodore
Seal 22 owner in the 1990s
now Sophia P275