Dutch Flat Mates (Sky Scrappers): A Tough Dutch Flat Mate Sudoku Variant

Today's Puzzle:

Is all about Skyscrapers, not a common sight in the Netherlands, perhaps that is why this is such a difficult puzzle!

Link to Play Along:

Dutch Flat Mates (Skyscrapers) by GoodCity http://tinyurl.com/SudokuSleuthDutchFlatMatesSky

Rules:

Normal sudoku rules apply.

5's live in Dutch Flats: All 5's in the grid must strictly have EITHER; a '1' directly above it AND/OR a '9' directly below it. It may have both, but it doesn't need both.

Skyscraper : Each digit in the grid represents a skyscraper of the corresponding height. Clues outside the grid indicate how many buildings can be seen from that direction, where higher buildings block the visibility of lower buildings.