Logic Masters Deutschland e.V.

Previous Dutch Flat Mate Puzzles
This has been a weekly series since '18 Oct 23'. Here is a spreadsheet link for all the previous puzzles in the series, which also has a few teasers for upcoming constraints/guest setters in the series (subject to change).
This alternative link offers a limited LMD search for Dutch Flat Mates.

Special Thanks
This puzzle was a collab with palpot, using a constraint that I believe jovi_al created.

To play the puzzle, please click the image:

Initial Setter Difficulty: 3.5 / 5

Normal Chaos Construction rules apply
Each row, column, and to-be-determined 9-cell region contains the digits 1-9 exactly once each.

Dutch Flats
Every 5 in the grid must have a '1' directly above it or a '9' directly below it. It may have both, but it doesn't need both.

Boundary Sums
Clues outside of the grid give the sum of the digits that appear in the first group of cells seen from that direction in that row or column, ending at the first region boundary.

Hint to start

It's worth considering min/max sums by number of cells throughout the puzzle. There are a lot of low digits in the top left, ensuring no repeats within regions is key. The 15 clue down C2 can help with this. Don't forget Flat Mates!

Visual Example
To play this 5x5 puzzle, please click the image:

Guest Setter
Whose pot? Next week palpot again, but without me!