I did not get a chance to see the big cross cut saw in action up close, I was chopping the same cut on another piece at that time. I remember I had a flash of panic at one point while chopping, I almost split one of the little corbels, I checked myself just in time.
I wonder if you clamped or screwed a scrap over the timber and started the saw in that piece, got the teeth into the kerf and just kept going. draw the lines needed, it could be a bit choppy to start and on or off the starting line but with the kerf started by the time you get to the real line you are on track. But it is extra steps. Similar to what Gabel mentioned, you could use to pieces one for each side of the cut with a set of quick clamps it may go fast.
Ever see big timber chopped at the shoulder?
Tim