Folks, just to be sure. 'Muiderberg' was invented some 35 years ago by two Dutch players (Onno Janssens and Willem Boegem). By the time I started to play with Onno I called those type of openings, I gave it the name of Muiderberg, a small town near Amsterdam where Onno lived. Mid nineties I wrote a book on the Muiderberg (in Dutch though) merely due to the fact it was getting very popular in The Netherlands (we even won WC's with it). And yes, Muiderberg are much recommended to open on 5 (no 6) M and 4+ m. Jan van Cleeff