1525's engine is back in the frame and soon to be restarted. As promised, here is the information for the knowledge banks of future owners:
The engine is supposed to be installed and removed from the right side of the motorcycle.
To do this, the battery box needs to be disassembled and removed from the left side of the bike. The shroud below the fuses and above the battery also comes out at this point. It allows some up-down movement of the engine. The right side electrical box can be left in the bike but, you'll end up taking a bunch of the connectors apart to make clearance anyway.
After all the connections are taken off the engine, it would also make sense to wrap all the frame rails with pipe insulation as I've done in this photo. They were all zip-tied in place to keep them from moving.
Finally: the keystone: remove the two bolts holding the starter motor and remove it from the engine. That little bit allows the engine to move forward in the frame and to hug the right downtube as it's tilted and removed.
The engine drops down slightly in the frame, then tilts to the right so the cam boxes clear the top tube. From there, you lift upward and toward the right of the bike, while still hugging the right downtube with the cylinder. The front and rear of the engine WILL come out and you can do it without damaging anything if you pad the frame ahead of time.

Reinstallation is obviously the reverse. I steered the front cylinder into the frame at an angle. Once it bumped against the padded downtube, I swung the back of the engine into the frame opening. Once in the frame space, drop it down between the two cradle tubes. It will sit down low enough for the heads to tip into place. From there, the engine needs to be raised to final position and the mounts reinstalled.