Here is the problem modifying the stock cover or likely injection mold, the cover as it is is weak and there are numerous reports of them cracking (without modification) mine included, The Injection mod will be a Acrylic version most likely and will be brittle and prone to cracks. The 3D printed ones use a Plastic/Nylon composite that is very strong (it has to be for the printers not to crack them). So buy the 3D versions. Considering the cost when the acrylic one will crack the higher cost of the 3d printed ones is a bargain.
Those that are worried about opening size the Nylon plastic that is used for the 3d printed ones is easily modifiable to expand the opening