Pagination in Score Window

I'm curious why using simple OS keys such as PgDn give such varied results. I realize that I complicate life for Europeans because I use North American Letter size as my default page size, but that really shouldn't be a big issue. I find that if I reduce the score window to 84% it works more consistently, but the program itself really should automatically size itself to the paper size being used (including the thumbnail view at the bottom.) If I don't make all these adjustments, the pages will bounce all over the place going out of view in surprisingly odd ways... I realize A4 is the standard generally used in the music publishing industry, but there are a lot of folks this side of the Atlantic to consider...

Thanks,

Ian