Im not sure how big you can bore the case but Im sure you could easliy go out to 100 mm. A friend of mine is running an Oxyboxer with 4 inch chevy pistons.
Sorry about that...I wasn't clear enough with the question I was trying to get across. I know that there have been 100+ mm big bore conversions, but I was trying to convey my interest in understanding the prevailing opinions concerning big bore kits for the wasserboxer.
A while back we had an individual contact us who posed an interesting point that an aluminum cylindered wasserboxer would greatly improve the inherent expansion that leads to water leaks by making the longblock 100% aluminum. Our flexibility in manufacturing these big bore kits would allow us to offer a multitude of bore sizes, from mild to wild.
As far as piston selection for use in a big bore application, you might want to look at some of the Keith Black offerings to see if there are any compatible pistons. As a matter of fact, we can design a custom piston and have it made up for most any application and typically no two sets of pistons are the same since we tailor each sets to our customer exact needs and desires.
Take care,
Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance