....you can put your plants into flower any time you want! As far as how much will you yield? This is an impossible question to answer, espically without visuals. However....I've grown your super silver haze, it's a very long blooming plant, IMO...it yields goods, but it will be almost impossible to predict your dry weight due to all the factors involved. Super silver haze should triple in size during the bloom process. If you utilize co2 at the appropiate levels (1500 ppm) this would greatly increase your yield. If your temps stay within range, you'll get an optimal yield...exc...exc...exc...it goes on and on....
...but, one thing is forsure here. Your only using a 400w HID. A good rule of thumb, (without CO2), 1/2 gram per watt if you done everything right! ...anything more you made your plants really happy.
...one thing every grower learns the hard way is, everything has to be optimal to get the yield estimate that you read about when you research your strains.