Bunch more done on the engine bed. The insides of the openings have been taken out to final size and smoothed with a long end mill
Then went around the outside and took the top down partway, to where the angled gussets will stick out. The screws were taken out one at a time as this work went, each replaced with a shorter one when that section was done. On the near side the cut was straight across the length, on the side away from the camera it went out and back around the extensions to the openings (which are to give the cranks more room) as well as a block in the center which will become a support for an angled brace up to the engine blocks.
Then started taking the top surface down to the final height, here its halfway done:
and all the way across
Then laid out and cut the side away from the camera down farther, that side has a lower height except where the post supports are on the two ends
Next steps are to take the sides down to leave just the low flanges, leaving the gussets at the ends and one in the middle. Here is after first set of passes on one side, taking it down as far as this end mill will reach. Will come back and take it down the rest of the way with a longer one. Again, the screws are being taken out one at a time while working across that portion, and they are being replaced with shorter ones as it goes.