Yes. Save what works first, though.... :P Just change your frame total field back to 30, drag the slider there, and either load or create the new pose. You should have spline interpolation on by default, so Poser will figure the time curves for you. Drag the time slider back below 15, and hit play to see how the body parts move. You may have to tweak things, depending on what the change is. If things look all right, then re-run the cloth sim, and make sure to change the settings to match the animation frame settings.