So, after almost a month I finally managed to install my kitchen. I learned an immense amount about kitchen furniture and had to do many things multiple times, but Behjälplig was really no problem. Attached are also my experiences.
Background: I wanted to buy a large-capacity dishwasher and have a space of 90.7 cm up to the top edge of the countertop. I also wanted a 4 cm countertop, so up to the bottom edge 86.7 cm. The large-capacity dishwasher just fits in there. The Miele can do 80 cm fronts without aids, but that was too expensive for me. BSH has the Vario hinge, but the only dishwasher that was an option for me due to the combination of functions / energy / water consumption AND Vario hinge cost 1200 EUR instead of 600 for one without Vario hinge but with everything else I wanted.
I had hoped for the "Stefan solution," but in the end reality caught up with me and I installed Behjälplig. In retrospect, it became very clear to me that there were very simple mathematical principles behind it.
Regarding the Stefan solution: The front would have to be set so high that, measured from the bottom edge of the dishwasher, only the maximum allowed overhang of the dishwasher remains. In my case, that would only have worked with a normally high dishwasher, not with a large-capacity one. The rule of thumb here is: the dimension of the front minus the allowed dimension must not be greater than the countertop’s bottom edge minus the minimum height of the dishwasher. The dishwasher is simply placed as low as necessary, and filler pieces are used between dishwasher and countertop so that it can be nicely braced with the countertop.
Regarding the mounting of Behjälplig on the existing screw holes of the dishwasher: You simply unscrew the short screws from the inside of the dishwasher and replace them with long screws supplied with the dishwasher. These screws are actually meant to hold the front; with Behjälplig they hold the two wooden boards on the left and right, onto which the front is then hooked in with metal rails. Regarding the IKEA expert’s note that Behjälplig might be too short to use the lower brackets: Yes, that is indeed the case. I didn’t even use the lower brackets. The boards of Behjälplig could have been somehow extended, but that didn’t seem worth the effort to me. Even if you screw on a normal front to the dishwasher, the connection basically has to withstand tension mainly in the upper area of the door handle. Down below, no great forces act anyway. Therefore, I assume that Behjälplig will work with any fully integrated dishwasher.
By the way, the weight of the front is probably not the problem when using Behjälplig: My door really stays put at any angle. It is actually almost too stiff for my taste.
I also took a few photos (in my personal album; unfortunately, I have no idea how to link the photos directly in the post), so you can better imagine how it works.
Good luck to everyone who still has kitchen installation ahead!