I have the same case. I don't recall any specific problems getting the eject actuator to work. As an aside, I did have problems with the drive flaps sticking closed and not opening when the eject button on a DVD drive was actuated.
Its hard to tell from your picture, however, in my GD08, the arm that has the button on it that is intended to press the eject button on a DVD drive is plastic. If it is also plastic in your case, what I would do is either get some fine sand paper or emery cloth and lightly sand the top, and the bottom, towards the left edge of the bar that the actuator slides on, just enough so that the actuator will slide to where it needs to be in order to press the eject button on the DVD drive. I would not sand the face of the bar as that is detented and is intended to lock the actuator in place (as I'm sure you know). If emery cloth/sand paper is not aggressive enough, I would possibly use a file with a "fine grit" face to do take off enough material on the top and/or the bottom of the bar to get the actuator to contact the drive's eject button. You may want to concentrate on taking an as equal as possible amount of material on the top and the bottom of the bar to keep the actuator properly in contact with the center of the bar.
FWIW, I started using the GD09 case mainly because it has an external USB-C port and I upgraded the CPU/MB for my HTPC. I don't like the GD09 because Silverstone made it smaller from front to back to, ostensibly, fit on a HT equipment rack. This fact makes that case a PITA because my DVD drive overhangs the MB in such a way as to allow only a very minimally sized CPU cooler/low-profile CPU cooler and I'm struggling to find one that both works and has a fan that does not make noise under higher CPU loads. In addition, my HT equipment rack has more than enough room for a case that has a more full-sized front to back depth so, IMO, Silverstone did something they thought would be helpful, but did not investigate enough to determine if it was really needed and would not cause other problems.
Silverstone seems to be the only manufacturer that makes HTPC cases, however, I get the impression that they never really think through their HTPC case designs such that there is not some problem with them, or those cases need some modification(s) to work properly. For instance, the DVD mount in the GD09 has holes to use to mount the drive that are simple, round, holes. On the new Pioneer UHD BD drive I just got, there is only one hole on the mount that lines up with the mounting holes on the drive. WTF Silverstone. Slots would have worked much better, IMO.
Anyway, good luck with the drive actuator. I don't think it will need much modification to get the actuator to where it needs to be.
