I finally took my newly built bike out for a test spin, about 9 miles. Coming from my carbon roadbike, I am shocked at how much the fork flexes when the front brake is applied especially considering I'm a short guy and only weigh 120 lbs. I've disassembled the headset twice and re-adjusted/torqued everything and there is no play in the headset. You can even see/feel the flex when gently rocking it back and forth while applying the brake.

This has me a bit freaked out because it I've never experienced this, even as a kid when I used to ride cheap steel BMX bikes. So I have a few questions, hope y'all can help.

1. Will a headset with sealed/cartridge bearings lessen the flex?
2. Even if it's normal, I'm worried about the fatigue on the fork/steerer tube. Can I eliminate the flex by using a carbon fork? If so, does it matter if the steerer tube is alloy or carbon?

FYI it's a new steel frameset with a new (but cheap) Neco headset