Having just received the Multicart I can confirm that the dimensions are ultimate for my own Lynx 2. What I mean by that is that my Lynx suffers from bad cart contacts and most games I have to pull out slightly to get to work. Some are worse than others. However your multicart works 100% of the time when inserted fully as it should.
It's a a shame all my bought games don't have the same dimensions.
So to stay on topic it may be good if the Flappy Bird carts are made to the same spec as SainT's
Regards,
Coope