My trekking pole is a Black Diamond as well. The locks have held up quite well considering how I abuse them. Note that it is possible to crack the plastic by tightening the screw way too much.

When going downhill, I think you have to grip the handle firmly to get any real benefit. At least that's been my experience.

I know cross-country ski poles are designed so the strap takes most of the force, but they are very long and so push you from behind.

When walking in rough terrain I need to brace myself from a full range of angles.

For a walking pole, I remove the strap entirely. I think it's a bloody nuisance, but that's just me.

I also remove the rubber/urethane tip when walking. It's great for the car and for shipping the pole in luggage. The carbide tips can be sharpened with a diamond file or a small grinder like a Dremel.