Originally Posted by MichaelW

It's an old fashioned solution to stiffening large frames back from when the only tubing was standard 1" diameter. It also allows a large frame to be built in a lugged fashion.
If you are looking for a particular style, its an OK solution. If you want the optimum design, it will have to be in welded, oversized tubing.
An oversized head-tube using a modern standard size will be stiffer and require less support in the large sizes.