Get a different wheelset. The better built wheelsets will have better hubs. The aero rims will make a difference too. Even at 125 lbs, you will notice the difference on those long descents. When PSIMET built my wheelset, I asked for White Industries hubs.

If you're light in weight, and the tires are over inflated for your weight, the bike gets jumpy and on a descent, it spells danger. There's that harmonic thing going on and the frame will tend to shimmy and you lose control. I'm not as light as you, but I do watch the tire inflation and also use my knees to create a damping effect so that the frame doesn't get that harmonic thing. This way, I feel comfortable going 30 plus mph on a long descent.

And I can stay up with the bigger riders.