Also, just wanted to say that you can select a vector line segment by having that layer over top of a blank normal layer. You merge the top vector with the bottom normal layer and Voila! You're vector is now a normal image and you can use the normal tools to resize it however you want. ^_^ Hope that helped/made sense. It's how I always do it.
" to apply the transform tools to a selection on a vector layer requires a non-obvious additional step. After creating a raster selection by whatever means, the user must click selection on the menu bar and then click either select points or select strokes from the drop down menu after which the selected points are highlighted and are affected by the transformation tools as expected. Those points remain selected until the menu is opened again and clear selected points is clicked, even if another raster selection is made. "