Take a look at the On Application Start interaction. You could position your first state outside the artbaord, then use that interaction to change the y value of it.
Thanks Chris! will have a look, though my app is bogging down and crashing a lot (I've
got 12G of memory). Guess i was hoping I could stick a line of code in the main/index.html file!
Thanks Chris,I eventually just increased the size of my art board in the y axis, did a Ctrl A on all the elements and nudged them down to the bottom of the artboard. I repeated for every state. The background colour of the artboard is the same as that of the screen background, so it's effectively invisible.