I had the Dutchman system on my Legend 35. Always worked reasonably well, and work best when everything was adjusted well. Spacing of the attachment points of the Dutchman lines on the topping lift is critical, as well as overall length/tension of the lines. When you release the halyard, and the boom drops, if the Dutchman lines go from slack to taught, then the main will drop nicely flaked. I eventually change the system so that in the winter, when I removed the sail, I would also remove the whole topping lift line, and the Dutchman attachment points would be removed together and folded with the sail. This meant that no adjustment would be needed next season (except for wear and stretch)
My sail did NOT have the official plastic thru-sail grommets from Dutchman (with the oblong hole), but instead just had brass grommets. These did not work as well. They bind a little because the path through the sail was not fair, and I had to use McLube on the Dutchman lines to keep things sliding smoothly (usually only an issue when hoisting in light air).
My new sail is a higher performance sail, and my sailmaker sort of begged me not to put holes in it for the Dutchman system.
So, at the moment, I've got nothing.
Chris