Who the hell told you to crouch to deal with speed wobbles on a longboard? That's the worst thing you can do at that level. All it's going to do is put your body in a position you're less comfortable and therefore even more unbalanced in, and make you go faster to boot. Crouching to deal with speed wobbles should only be done by people who are already extremely comfortable crouching at high speeds- that is, people with enough practice that they likely aren't getting speed wobbles anymore anyway.

To anyone reading this: what you should be doing is keeping your weight forward. As much weight as you can comfortably place on the front truck- that's where you want your control. Stand comfortably and build your speed up slowly. When I started doing big hills I was stood almost straight up. Don't bomb something when you're not even sure you can ride it. Oh, and while we're at it- learn to brake, get a spotter, and for fuck's sake put a helmet on.

There are changes you can make to your setup to prevent speed wobbles, but they also prevent you from learning from your wobbles. I avoid them. Just keep your weight over the front truck and stand comfortably.

ONLY crouch when you want to go faster. That's essentially the only thing it does.