I discovered, that 'stack' has a extremely poor performance (maybe augment as well). Please take look at the screenshot. Thinking about replacing stack, but that would be an awful work, and most time not an elegant way.
stack & augment take material time. The nature of the project dictates. Observe 'U' in red ... that does your project 0.06 sec [Smath 6179]. Read the "random fill" work sheet.