If you've gone from 55 watt bulbs to 100 wats bulbs you haven't just doubled the light output, you've also doubled the heat.

If you must use the 100 watt bulbs, then you're going to have to cool down the back of the light fixture, or find some way of creating a more heat resistant connection. When you've done that, you just have to hope that the reflector and lens can cope with the heat, too.

Good luck!

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Cheers, Neil