If it doesn't fit properly, my suggestion is to return it and exchange it for one that does fit. You might have to buy 2 reflectors to attach to the rear forks, one on each side. Reflectors are pretty cheap. If you intend on night riding, you can also attach vertically oriented lights to the rear forks.
43 km in 2.5 hours is good going. Well done Melissa, you'll kill 'em on the big ride at that rate.