The mounts were fully welded and looked great, although most people will never see this part of your bike.  If you don't have a fancy TiG welder, you can use a gas or wire feed welder and a little extra time spent grinding to achieve similar results.  You want to make sure you spend enough time cleaning up your welds, as you don't want extra weld material hanging down and distorting the silhouette of your tank once it is welded.