HMI spike is only true of lights with a magnetic ballast. HMIs with electronic ballasts actually ramp up to their true voltage (which may be higher than you would think).
In the link below there is a plate from a 1200w HMI ballast. The Pmax is what you have to worry about as that is volt-amps apparent load, which is a function of the load plus the power factor (without getting to in depth, power factor tells us how much extra power is required to run a light.). The Pmax is 2290 meaning at 120V, 2290/120=19Amps. You're not going to get anything else on that 20A circut, and can't run it on a 15A circuit. If you run stingers to it, your voltage may drop as well, which could make it not even run on a 20A circuit.
If your ballast is electronic power factor corrected (it won't always be, check when you're renting), most likely the Pmax will be lower.
Electric cable should never be over under - over over clockwise only. DMX cable depends on the best boy.
You always know which stinger came back from the camera department.