Help with tail boom fin on HK450 GT belt drive

Hi,
     I'm having a bit of an issue getting the tail stabilizer/fin assembly together. The screws that sandwich the fin to the mount around the boom don't seem to go in deep enough to hold the assembly tight. I don't have much for shorter screws sitting around unless a) I accidentally used them somewhere else, or b) I take some from the spares kit, although I'm not sure if there are any short enough in there. Any tips on getting this together ? Here's a pic for reference:



Note: The screw in the pic isn't in all the way in this shot, I just took it for reference. It goes in much farther, but still leaves more thread exposed than the thickness of the fin shown below.

Thanks!


Kyle