I have seen lots of 16 wide and wider doors with the operator to one side or the other.
Installing a garage door opener off center.
The weight of a garage door is supported by the door springs cables and pulleys not the opener.
Garage door openers come in several varieties.
Attach the straps to the irons with hex head screws.
Follow the manufacturer s instructions to assemble the opener and mount the rail to the header bracket above the door.
Request service online in store or by phone and a licensed professional installer will contact you to schedule the installation date.
Use one piece as near to the top as you can which would be just below the strut.
Bolt the angle irons to a rafter or rafters with lag screws.
Place the opener on a ladder and use scrap lumber to get it at the height you need.
Prepare your garage door for opener installation.
If your door has extension springs the opener must be installed in the center of the door.
The opener can be installed within 4 feet to the left or right of the door center if there is a torsion spring or center bearing plate in the way of the header bracket or door bracket area.
Garage door opener installation is available starting at 127 including removal and haul away of old openers and other materials.
Align the opener s rail with the center of the garage door.
Make sure there is a strut on.
The only consideration is the door is balanced properly on spring tension.
If you can t raise and lower the door normally by hand do not install the opener until the door is repaired.
Attach the straps to the power unit with the hardware provided.
Then set the opener on a ladder where you re going to install it.
As you said run perforated angle iron from the center stile to the next stile over.
Go ahead and mount it off center and save yourself a headache.
To install the opener you ll need to hang another angle iron from the center joist on your garage s ceiling.
You can be off center with the opener provided the door has a torsion spring which it sounds like yours does if your door was extension spring the kind when the spring stretch along the horizontal track then it wouldn t work properly.
An opener will work ok off center of the door but really needs to be perpendicular to the door.
Chain drives are the cheapest but loudest option.