Here are the fets temporarily mounted to the heatsinks. I say temporarily because I forgot to add some thermal grease under each fet. But I’m glad to know that my dimensions were ok, and that everything fit nicely. I used double sided foam tape on the bottoms of the 3 heatsinks. This will isolate it from the board per Fritz, and mechanically secure it to the board.

Looks just like the picture! Shot w/G1.

Here is a closeup of the mounted fets. The screw heads just barely clear between heatsinks. So make sure when you drill and tap that you center the holes vertically along the slot. Using button head screws would give more clearance. My flat washers were a bit thick as well. Shot w/G1.