World partition map 50kmx50km problem

hello,

I have a problem. I want to make a landscape 50kmx50km, what would be the workflow to make it? I tried with landscaped height map 1024x1024 res and effects didnt satisfy me. the map was too flat.
how to get better res maps?

My second question is - why sometimes the world partition wont divide my landscape in to loadable tiles(after creating the landscape)? I dont have on a “word partition window map” regions to load. Did u have similar problems?