The 6 inches over the edge is the best way to go. You can tighten up the edges afterwards by ironing around and sort of underneath. Also I don’t use starch at all, just water. Starch hardens the edges and make shirts more difficult to work with in the future.
The last trick I have is buy custom shirts with all the same cuff and collar cuts, that way if you drill down ironing one, they are all the exactly the same. But that might be metrosexual overload. 
Really I can whip up any shirt in about 4 minutes, its just an excuse to buy custom shirts.