[dsraven]

Panhard behind axle, that's what I did. Should be as long as possible and sitting level at ride height. Less sideways axle motion with suspension travel when bar is level and long.
On the welds, it is fairly thick steel so you may want to bevel the edges and then turn up the heat just a little. Better penetration and with a flatter bead as well. Also, watch out for long bead runs that will put a lot of heat in a concentrated area and possibly cause frame warpage.