Darcy, I glue two wooden blocks to the front firewall just above where the steering arms sit when fully retracted. One on either side. That will hold the nose gear perfectly vertical while in flight. Make sure to leave just a hairs breadth gap, so there is no binding of the arms up against the blocks.

To prevent twisting while the gear is retracting, make sure the steering cable isn't binding on anything while the gear is in transit, causing twist on the way up. Make sure there is plenty of clearance in the nose gear retract opening on either side, and you will likely have to widen the slot in the former just ahead of where the wheel sits when retracted to make sure there is no potential interference with the strut.

Here is a pic of the nose block on one side of the Lightning I have handy ... works the same for the Flash.