I have six AJ heads and about a dozen Davis heads, none of these contra-pistons stick down out of the head, most run about midway of their extremes. Left to right are an Irvine .40 stock Diesel head, a Davis Fox .50 head, a Davis SuperTigre .40/.51, Davis MVVS .61, and an AJ Coholic MDS .78 head. All are about midway in their travel except the Irvine .40 which is near the botton of its bore.