I'd say that based on what you're saying, you're doing it right. I personally drop the weight to the top of my head, about and inch or two past my hair line, then all the way back up. I do close and wide grip sets.
Tuesday was my bicep/tricep day and most of my tricep sets were in the 125-145lb range. Are you using 45lbs per hand or the 45lb bar? If you're using the bar, I'd say step your weight up and get a spotter just incase. Like I said, you gotta be scared of dropping the weight to build.
But remember, form is everything. Do it right, or don't do it. Just do it bigger.