David, The method is to put the pipe thru the flange. I've attached two jpegs to show examples 

Bill Jepson

Bill;

Seems to me the tacks on the back side only add stress risers where you don’t want them; a place for a crack to start.  I suspect the practice of doing that is as an easy way to ‘locate’ the tube to flange.  I think it would be better to fixture it some other way, and eliminate the tacks. Ya’ think?

Al