Hi Neville.
I have never trusted the plastic bracket system to last for a long time.
So my solution is to put another front piece as in the picture.
Yes I know, another 12 edges to be edged for a 4 drawer bank, and they have to be cut over size to go through the edger, then re cut to the height to suit the front.
And more assembly time.
But its worth it so we don't have to go back for warranty.
After Installation when all the drawers are tickled up, the last thing is to lock them off with the two screws.
The trick is to make it high enough or low enough so that the handle screws miss the top of it. (more pain

) Higher and the handle screws add more strength to it.
I did have a template for the guys to sand the curve to on the sander but it seemed to be more trouble than it was worth.
I'm not so keen on the gap it leaves when the cutlery insert is put in, but touch wood I've never had a customer complain
I haven't used Blum for a while so I am not sure of the profile, and the Hettich ones have a curved profile on them, but either way I imagine you should be able to apply a pattern to both ends to the front of a drawer box in the part editor and constrain it.
I have seen others use the mini angle bracket solution under the base of the drawer as well, but yeah, Its not holding on up in the middle of the drawer where its need more.
That's my 2 cents worth, I'm sure there are other solutions out there.