Just getting a reflective surface on the inside of the "hood" doesn't give you a good reflector. A good reflector lets you see a complete image of the bulb on each side of the bulb, so it appears like you have 3 bulbs, instead of one. That requires the reflector to be shaped correctly. The AH Supply reflectors are shaped right, and they can be slightly bent outward or inward to fit better, but it won't work well if you make them fit against the sides of the "hood" without regard to the shape of the reflector.
What are the tank dimensions? Unless it is a tall tank, more than 24 inches tall, two T5HO bulbs with good reflectors will be too much light for a low tech tank.