My RS II grilles were broken when I bought them last year and had been repaired with the old glue and popcicle stick repair job.
Of course they broke again shortly after I got them.
I tried a couple types of glue, tried metal strips and screws, also built some screen moulding outer frames for them which I tried to attach using 2 or 3 different staples/staple gun nails.
The old particle board was just not receptive to any sort of fastener I tried, usually just cracking or crumbling the material.
In addition, my experience is that once they are broken and repaired theres a 50/50 chance the alignment is off a bit which can make lining up the 4 attachment holes a little difficult.
I did finally get the screen moulding to attach well enough that I can remove and replace the grilles without them flopping over like a cheap lawn chair.
Page two of this thread shows a picture with the "frames" around the grille...
http://www.audiokarma.org/forums/in...me-bigger-infinitys-for-a-while.713134/page-2
I did restain the frames to better match the OEM Infinity color after that picture was taken.
Like totem mentioned, the best solution is probably new grille frames made from a different material.