I did it, very simple mod. You will need a dremel to cut out the 45 degrees recessed area, long enough to cover all the 5 lower sata ports.
Use some masking tape while the motherboard is still Inside the case, place that tape on the recession slope, and make two marks on the tape with a felt tip pen (a good small Sharpie will do a great job) at each end of the sata port area, leaving some additional space at the ends, to facilitate sata cable connections. Then take everything outside the case, and I mean everything. EMpty your case until it is back to when you pulled it out of its shipping box. You must know that since you'll be cutting metal, there will be some metal dust and scrap.
Use any good rotary tool with reinforced cutting disks to cut out the metal. While your case is empty, you should put some more masking tape to cover the area you will cut, draw with the felt tip pen some line to help you guide your cut.
On mine mine I began in the interior of the case, cutting where the motherboard tray and the recess join together. Do not use too much force. Works better with a flex extension. Begin by gently creating some king of a groove where the metal will be cut. Do not push too hard. Use 3/4 to full speed. For the upper part of the recess, turn the case on the other side. It is much easier to cut when Inside a fold then over it. To cut the sides of your SATA port window, just put the dremel disk in the middle of the line and slowly apply pressure, at max speed, until you have cut through the metal. Then when it finished, you can take out the piece of metal and there is your window. Now you might want to clean up with a sanding stone, I used the conic one. The reason is to soften the rough edges created by the cutting of metal.
The beauty of that mod? You can plug your bottom sata cables using the L shapes end, a very clean way to install SATA cables,
Some pics to show you how it looks (not perfect, it was my first take with a dremel, but not so bad after all)
There you go, you now have a fully E-ATX compatible computer case, especially those that are just a bit larger than regular ATX. As you can see, the G1.Sniper3 just barelly fits Inside the 400R. With the mod, it now can be fully used.
To get a better look, I could use some C-shaped automotive strips. But if you take examples from Inside the case, there is only bare metal where your 8-pins CPU power plug is coming out.
Next mod: cutout the left side panel and make it a see-through window like more expensive case.
Edited by MOG Hammer - 5/19/13 at 3:36pm