just ran 7 tanks through my XXL3 today a few things i noticed:

-is the piston smaller in the XXL3? as when i went to open up the engine the piston and conrod just poped of the crank pin when i tiped it upside down. i've never had this happen with a new never turned over engine.

-the sleeve on the XXL3 seems to have a wider top lip, the screws from the heatsink have a half moon cut out on the lip of the top of the sleeve.

-the XXL3 seems alot easier to break in than the SL3. the piston does not lock up like a MF whenever you go to start it up. infact you don't need a hairdryer to start up a new engine like you needed with the SL3 when it was new.

-the XXL3 only has a .1mm headshim! i added another .5mm headshims just to be safe. Ran fine, broke in pritty easy with this setup.

it is still runing rich-ish and it is ready to be race tuned.

break in proceedure

-idled for one tank at factory setings (wrapped head in aluminium foil, kept it at 90 degrees celcius)
-idled for half a tank (wrapped head in aluminium foil, kept it at 90 degrees to 100 degrees celcius) then bliped the throttle for the rest of the tank on the bench (Factory settings, no alfoil)

-drove it for the next 5 tanks on my home track with incremental adjustments to top end and a few touches of the bottom end.