No, that wouldn't help you out much.
Preloading is basically a fancy term for taking the slack out of a suspension component. So where a strut brace is concerned, you would want to tighten up the slop by putting pressure towards the length of the bar. The good aftermarket strut braces usually allow adjustment of preload via some threaded insert. You preload 'em on the ground by torquing on the adjustment mechanism, and only slightly as the amount of preload wanted is very slight (normaly).