A little backstory. The plant where I work has deemed the 100W medium base HPS bulbs as obsolete and does not stock them. I know they aren't obsolete but some pencil sharpener somewhere has tied his bonus to saving the cost of stocking these lamps. We have hundreds of these sized fixtures scattered all over the plant site, along with every other variation of every different style/size lamp invented. It is suggested I replace the perfectly good fixtures with Metal halide or LED fixtures. Which I do as I am not averse to changing a bad fixture with something more modern, but it angers me to tear out a perfectly good fixture, spend upwards of $700 on a new fixture and labor for a $10 bulb. Since we have an abundance of 70W HPS Medium based bulbs still in stock, what are the risks or pitfalls of using this lesser watt lamp in a higher wattage ballast? Remember, if it ruins the existing fixture It will be replaced with probably an LED fixture. Sunday night is lighting night.....yippee!