precision parking

All you need to do is line up one side of the coach. The other side will automatically take care of itself.
Decide which mirrors that you feel the most comfortable with and put a line on the floor using that mirror as the guide.
When it is time to back up just follow that line with the mirror and you will be fine. The worst thing you can try to do is chase mirrors and switch from one side to the other. As long as one side is where you want it, the other side will be also without having to actually monitor it.
Put some kind of block on the floor so that when your rear wheels contact it, you will know that you are as far back as you need to be. These can be attached to the floor permanently if you want.

Hang some tennis balls from the ceiling along the driver's side;or something else that may easily be seen that will not damage the coach. Place the first or last one beside drivers window to mark the stop point?

BTPO1 wrote:
You could use colored tape on the garage floor and follow the tape with the rear wheels as you back into the garage. Using the drivers side mirror that should be no problem. JMO

This is what I was going to suggest. We recently moved from the San Diego area to Lake Havasu into a brand new home. This home came equipped with a 15.5 wide x 53' long RV garaged attached to the two car garage. Prior to move in, while the house was still un-occupied, I authorized the commercial epoxy coating of all the garage floors.

And, I too need that coach to be almost dead center, EACH TIME I BACK IT IN, so that I can open the compartment doors and do work, retrieve things etc. So, while that coating was being applied to the floor, I had submitted to them in a drawing, two bright, 2" yellow lines, equal distance from each side wall.

Those lines are the lines that I use to back the rear tires right alongside. It works flawlessly. I can put that 36' rig, in the EXACT same spot, each and every time, in a matter of about 30 seconds. It sure saves from filling up that garage with diesel smoke from jockeying around trying to get it centered. Those lines, are epoxy paint, and, they are under the final two, epoxy clear coats. So, they will NEVER wear off. Hope this helps some. Good luck.
Scott

P.S. The mess you see in the back of the new RV garage is now gone, all that's there is a nice work area.

You could use colored tape on the garage floor and follow the tape with the rear wheels as you back into the garage. Using the drivers side mirror that should be no problem. JMO

Put a target on the back wall and a chalk line on your back up monitor. Also, a chalk line down the middle of your garage that would be visible in the monitor might work. Finally, after the RV is parked you could secure 4X4's to the floor to guide the tires into the correct position on the next attempt.

Other than those suggestions, I can't think of any solutions.