35% dimmer feature is a safe amount to run MH bulbs at. the following is a quote By Craig DiLouie
"Dimming below 50%: When HID lamps are dimmed below 50% of rated power, they may experience degradation in service life, efficacy, color and lumen maintenance, or they may extinguish. Dimming below 50% of rated power, in fact, may reduce high pressure sodium and metal halide lamp life by 90%. As a result, dimming below 50% may void lamp warranties.
NEMA recommends that the maximum recommended dimming level is 50% rated lamp wattage for both metal halide and high pressure sodium lamps. NEMA further recommends that the lamps should be operated at full power for at least 15 minutes prior to dimming (unless the lamp is extinguished from a voltage interruption and the input voltage activates the timer, in which case 30 minutes is recommended before dimming.)" | 
