Hi Eddy,
If I remember correctly, the Yaesu and most major Japanese radios use the JIS standard hex screws ( slight difference in size and taper angle). I've used the standard 1.5 on my 817ND and it came loose very easily. Sounds like yours got torqued down a bit tighter. Use at your own peril, but a drop of WD40 applied with precision should do the trick (it worked for me on a stubborn case screw.)
