[oldbluesplayer]

looking further, I think I know where you are coming from, that most of the motor force forward thrust load is carried by the transom at the edges, into the hull - kind of similar, in reverse, to the transom test people talk about, standing on the tilted motor to see if the transom flexes under the weight -

both views are expecting that the transom is an unsupported, or marginally supported, span, attached primarily at the ends, kind of like a simple bridge, except that the transom is also attached to the hull bottom, so it is more of an oil can flex - imagine cutting half of the top out of a 55 gal oil drum, then grip the edge, in the center - it would move up and down - any unsupported edge would do that -

It seems that cracks primarilary start to appear at the lower corners of the transom motor well cutout - leading me to suspect that most transoms are not adequately reinforced by inherent design, so that as soon as the core wood gets wet and begins to lose it's stiffness, the load is shifted into the glass, which if not overbuilt, soon begins to fail under the increased load - thus the cracks forming.

Imagine a straight line, width of the transom, fastened only at the ends. From underneath the line, you have a force, up against the line - now add - above the line, imagine a structure in the letter "W" sitting on the line, above it, in the center - the two bottom points of the W are on the transom line, the two upper points of the W are fastened to the boat hull - either directly or indirectly thru the cap -

the more strength in that center support, the better off the whole transom structure will be.

just my humble 2 cents worth.

Bill