Exactly....
On the Silver Slug, I always keep the 4th Gear OD locked out on my A43D Automatic, unless I'm on the freeway, or doing at least 50mph. The 3rd gear 1:1 ratio works the same as our 4th gear on the W58, esp if I have to panic stop. The "engine braking" that 3rd gear provides helps allot. I've had to panic stop the Redpra in 5th gear at least 3 times in the last 13 years & it's not a whole lot of fun....
Plus on the Slug, if I keep it in 3rd gear @ medium cruising speed (35 - 40mph), then the tachometer is near 3K rpms & if I step on it, it will go up to 3,400 - 3,600 rpms, which is right at peak torque for the 5ME motor. Comes in handy for passing acceleration. Below 2K rpms, it's a little slow to accelerate.
If you at around 40 mph, just keep the OD locked out & let the powerband turn on at around 3K rpms on the 5MGE. Helps w/ acceleration. If you have the OD unlocked, then it's just going to take a tiny bit longer to start accelerating, because the tranny has to downshift from 4th to 3rd.
Then again, it also depends on your driving habits.. Your's may vary, I just listed mine.