Question about stacking lights

I am going to hang a 400w MH bare bulb vertically in veg. I want to add a 600w HPS during flower and place it above the MH. What is the best way to safely do this? My first concern is the HPS bulb melting or damaging whatever mechanism is holding the MH bulb.

i'm interested in what feedback you will get. i myself would use something to hold the bulb from the side like an arm, but maybe there are better ideas

I googled vert grow and found this.
Heres a link to the page it came from~~~~ http://www.420magazine.com/forums/plant-bud-photos/176868-my-take-green-bastard-s-vert-grow.html
Good luck.