Reflectors catch about 20% of the light from the COBs. The rest is already within the 90 degree angle. On the other hand, COBs with reflectors lose about 10% of the total light (even more when used for a while). So they actually lose about half of the light that they are supposed to send down to the plants. You are much better off just letting that light find it's way to the plants on it's own.
You will actually see more penetration from shallow angled light than from light that goes straight down. If you have a filled grow, look at your canopy from straight above. Pretty much a closed green field. Now look under a shallow angle and you can see right between the leaves.
Malocan showed he had 20% less light with reflectors over his grow area. This is because you don't just lose light on the reflectors, you also need to increase the height of the fixture to still get a uniform light distribution. That means more wall losses and therefore more light lost due to using reflectors.
@HideousPenguinBoy, You really don't need to know the distribution pattern of a COB (it's in the datasheets though). All you have to do is to distribute the COBs as evenly as possible over the grow area.
When you finish your light you can get the uniformity you want by adjusting the height of the fixture over the plants. When you go too close you get hotspots. Just keep increasing the height until you see a uniform light. I use around 12", but it depends on the light intensity per COB (many small ones will need to go lower and a few big ones would need to be higher up).