[Wildcard-1]

Jenning's book is a very good wealth of information for novice 2 stroke tuners. But some of the information is slightly outdated with advancements in materials ect.

On the subject of rod length and stroke vs bore:
While adding bore adds more displacement and theoretically more available power per mm than stoke, the addition of stroke allows for more linear power stroke per deg of exhaust port open time. This allows for more aggressive porting while still maintaining or improving the amount of low to mid power. While adding bore can and does in most cases add a noticeable power gain it can in many common two stroke applications rob you of valuable transfer port volume. The gain of adding bore to an engine is largely dependent on that particular engines paramaters. As far as rod length is concerned, long rod motors tend to rev slightly slower than the short rod variants. But, they are more reliable due to the decrease in piston side loading they create. But to that point a certain ratio of rod length per stroke must be kept, so optimum rod length is also dependent on an engines perameters.