You could look at the two different targets as "states of tune". Professor Blair uses examples in the text of some of his two-stroke books, ranging from GP roadracers to off-road.
If you give me an example engine, I'll tell you time area values that work and why for that particular engine application. Just look at the differences in engine specs between an Honda RS125 roadracers and a CR125.
You guys are encouraged to check out some of Professor Blair's writings, you can search his name at Amazon; ( Blair, Gordon P.) or at the SAE's book store
www.sae.org
My three favorite Blair books are
PT26, written in the late 1970s, a collection of research papers performed at the Queen's University of Belfast. The best paper was one about transfer duct shape and profiles for scavenging efficentcy and different powerbands.
Design and Simulation of Two-Stroke Engines, written in the late 1990s, this book focuses on the use of simulation programs for individual components and working all together.
Design and Simulation of Four-Stroke Engines, written most recently, this book features cases studies of engines ranging from world superbike to IRL. This is a thumper guys' bible. It will take you 10 years to read and maybe you'll understand it. Very technical and expensive but worth it weight.