Here's my thinking. The entire top edge of the transom is an exposed Plywood edge. I KNOW you did a GREAT job of saturating it with the OT recipe but, Once you cap it condensation can and will occur under that cap as well as water will get under there. That cap will probably move around too and abrasion will occur. I'm overly cautious about plywood edges soooo, If it were me, I'd coat that entire top edge with a thin to medium coat of 4200 and let it cure. I'd then bed the aluminum cap in 4200 when I placed it on the transom top to hold it in place. Of course any fasteners you use you'll need to predrill and coat them with sealant as well. As you say, I'm NOT a Tinner, Never have been, but if and when I do become one, That's how I will do my transom.
For any future NEWB's EEEEEEpoxy IS the best and most costly method for coating and sealing the wood on your transom. The method Frey0357 has used on his, IMHO, is the next best method for sealing a wood transom and a lot less costly. With good maintenance and care it should last several decades.:nod:
