Vti-chris, I am not sure what you mean. The factory has made a few changes to the heads and deck ht. reccomendations do vary from location to location. Since I have been importing the engines there have been only 3 deck ht. changes. The first batch included 3 shims with a total width of .5mm, They then added .2mm into the button and removed 1 shim. so the overall squish was the same but the engine only had 2 shims with a width of .3mm. The final change is recent and they added 1 shim so the shim width is now .4mm and they include a extra shim for break in, but that is up to you if you wish to use it. The last change was to increase reliability by making the engines easier to tune and also lowering the risk of detonation because they were at the min. deck ht. for 30% nitro.

There were very few of the original deck ht. engines sold in the U.S. and all of them had the original alumn. carb. I currently run the middle deck ht. engines and have never had a problem, but a few people had experienced blowing an few plugs during break in because of the deck ht. I haven't had a single complaint from the latest batch.