Why just the modeling light? It won't perform any differently from a regular 100W desk lamp, aside from the ability to mount a modifier on it. If you have to use the modeling lamp, a WL with a 250W bulb would do better. Or you can use an E640 for perfect voltage calibration
An umbrella is probably the best choice for avoiding overheating. The 100W should be fine, the 150W will get pretty hot. Here's what happens with a 150W bulb left on full by a would-be assistant for about 10 minutes with the cap on.
