changing to 12-12 cycle

Ive been using a 400 watt hps bulb, but I also purchased a 400 watt metal halide conversion bulb. Should I use the conversion bulb to help promote flowering or just stick with the hps? How long will it take to being flowering? Ive only been on the 12-12 cycle for 4 days now and haven't seen much difference yet....

you should have vegged with the metal halide light.. you want to use the hps for flowering........ you have only started 12/12 for 4 days so your plant probably hasnt even shown its sex yet. it will show sex in the next week or so...... you got like 8 or 9 weeks till harvest

so switch back to the hps??