DISAPPOINTING is the very least way to describe this. The Understatement of the Month.
I can see where a builder would overdo the RV length when trying to get away with stock wheelbase. Inexcusable, but I can see how that might happen. Our first Class C was a 24-ft on 158" and I think they should have used Ford's stock 176" version when they were adding a rear frame extension.
But what I don't get is why a builder who was already paying to have the frame stretched, would not stretch it ENOUGH. All I can imagine is trying to sync the wheel wells up with the floorplan. Being able to DRIVE the doggone thing ought to take precedence over the styling plan.
You've more than persevered. Genuinely sorry we couldn't solve it. Have a great time with your Class A! You may find it turns as tightly as the C. The E-Chassis doesn't have as much steering "cut" as the A chassis.