If you can get your pal to put a crease down the middle of the reflector above the tube centreline and re-form the reflector in a double parabola (aka 'batwing') instead of a single parabola, it will work much better.

A single parabolic shape will focus most of the reflected light right below the tube, where there already should be lots on the direct path from the tube.

A double parabola will shift the reflected light toward the outer edges of the coverage pattern, evening out the coverage significantly.

A double parabola shape will also duct hot air away from the tube instead of allowing it to collect near and just above the tube.