While the blade of the bulldozer may have been 8+ ft tall, it is clear from the pictures that the cab of the bulldozer is well above that, probably at 12 ft or so. It is clear from the second picture that the driver could see RC over the top of the blade, assuming the clear part of the cab is where the driver's head is at. The issue should be focused on this fact and not so much on weather there were any tunnels involved, in my opinion. Though the 4th picture is suspect, and appears to show a much larger blade than the other two pictures, the driver should still have been able to see RC over the blade, provided he actually sits above the top of the hydraulic assembly in the upper left of the 4th picture. I can't imagine there would be much use for a bulldozer that was built such that the driver could not see over the top of the blade in the lowered position. Maybe someone, in their volumes of research, can show us or comment on a manufacturer's diagram of the bulldozer blade vs where the driver sits.