That seems to be the best height, i have mine around the same and veg switch only. I still havent decided if i am going HPS or LED for the grow i have a choice but it depends on what happens over the next few days. I am finally showing sex on my other plants and am pulling all kinds of males, which is to be expected with growing regs and such. i dont know about you but it seems that those things are BRIGHT. Have you taken a look at what both switches do in that small space yet?