Dice reader for 18mm dice fail

It was BuildBrighton's Open Evening tonight and the reflective sensors had arrived from Farnell just minutes before we set out, along with some 18mm dice from eBay, so we took the whole lot along and designed our first dice reading device.

It didn't take long to discover that things weren't quite going to plan.
Namely the dice are too small, or the sensors are too large to work together:

We can get a line of three sensors to pretty-well line up with the dots on the dice. Where the two don't quite line up, we could take up any gaps by placing a laser-cut tray with the dice spots cut out between the dice and the sensors.

But when the dice is oriented the other way around, the spots and sensors simply refuse to line up.
We've already placed our sensors as close together as we can get them, on a single sided board (though even on a double-sided board, there's no much extra room between the pads).

No matter how much we twist the sensors around, we can't get the sensors and dice dots to line up. Which means we either need to come up with a different way of reading our dice - or maybe just buy some bigger dice to use with the game!