Validation in Finland
They are not know to do this. Finnish CAA has the brain capacity of an ameba. You are much better off by doing what ever is needed in Sweden. They will give you a chance to do all the exams based on the FAA ATPL after an assesment. The required amount of exams is 14. Once again the whole exam procedure in Sweden (Hurrit know something) is much more relaxed and lets put it nicely: Down to earth.
Finland will not issue a "National" or an JAA ATPL with a restriction to OH registered airplanes only like UK CAA does, because they do not have to. I know someone who has looked into this and he said that it was like banging your head against a brick wall. You might as well have tried to teach a horse to play Mozart.
You can PM me if you want the Email address for this gent who has all the details.