FWIW, I'm in the same boat as the original poster, although I have 80mm. I just bought a Keylab Essential 88, but can't really recommend it. After taking the caps off, it fits nicely, but the keybed action doesn't feel well – it's lightyears behind the playability of my "gold standard" (KOMPLETE KONTROL S61).
Of the 4 velocity curves, none fits really well, it almost behaves random.
I pondered about building a Doepfer PK88 directly in my desk, but according to the schematics which just came from Doepfer it is 84mm at its highest point :( So I have to continue looking.
@Robert Kooijman: Which keybeds exactly did you treat so well in the picture you shown?