OHHH, I see what you're doing. This could still work out. I see two possibilites to fit 5 halides in that canopy.
1) You can Turn the reflectors so that they run perpendicular instead of parallel. It looks like they will run into the VHO's though. Since you are running the 10K 20K combo then you might be satisfied with not running the VHO's at all. THe 20K's might be blue enough to offset the 10K's like VHO's, but from what I have seen in pictures the Coralvue 20K's are pretty white for a 20K bulb.
2) If you want to keep the VHO's and still run 5 halides then you can overlap the reflectors a little bit. Slide the one in the middle to the left untill the bulbs are almost touching or untill you have sufficient space to fit the rest of the pendants and reflectors. One more thing you can do is run the Reefoptix pendants Parallell to save on space. I think that these reflectors are meant to be run perpendicular to get the most efficient use of the spread of light.
Well, actually you might not have any trouble at all now that I think about it. The Reef Optix III's have a 9"x11" footprint. So if you mount them perpendicular then that should leave you a good 48" for the three reflectors you allready have. That's 16" per reflector. What are the demensions of the reflectors you have right now? They look to be about 16"
Just kinda spouting out idea's . I do still feel that the 10K 20K combo looks best when running an odd number of bulbs, unless a 10K and 20K bulb share a single reflector. But that's not applicable in your situation since you are running DE bulbs. But like I said earlier, when it boils down it's really just personal preferance and you will have to experiment with different combinations and see which you like best.