Mine cracked on the exhaust side. The crack starts at the base of the skirt and makes its way up through the two little oil holes. The 'standard' cast pistons that come with the kit are from a Kawasaki engine allegedly. I did the crank case mod and ran some cast pistons with full skirts for a while (because Matt@Tyga was struggling to get a new supply of forged pistons at the time) and they were fine when i took them out to swap over to the forged items. I should point out that mine is a dedicated race bike and therefore gets thoroughly abused as such. So don't panic if you've got unequal skirted pistons in your street bike's motor. If you want the piece of mind then the process of modifying your crank cases to accept full skirted pistons AND advice on how best to order them specially from Tyga are documented in an old thread on the forum here. Just use the forum search function.

I should also point out im not writing this as a direct reply to the OP but as a message to people using the search function to find help in future.
_________________
After years of moaning about immigrants now i am one...