Metal Halide for flowering? Uhm, no? Also, if you wanted to substitute for the UVB radiation the HPS is lacking, go with a 10% UVB fluorescent Reptisun light in unison with the HPS. Ed Rosenthal even mentions something to this effect on Cannabis Culture's site.

http://www.cannabisculture.com/articles/2091.html

http://4littlepets.com/index.asp?Pag...dID=14355&HS=1