Stovie
Drilling and refixing should be an option, I would try to find stainless screws try custom fastners .com and i would make the lugs from mild steel as the things shouldn't get hot enough to melt away too fast. Use the red gasket repair that motor mechanics use to seal the glass to the frame too this will keep the smoke in and excess air out and help things a bit. remember cast is hard outside and you may want to get a cobalt tip bit or if youre real handy reprofile the drill you use to have a sharper rake angle say 60 degrees instead of 30 this will help you get through the tough outer skin of the casting.
lastly as you have asked your question this way I probably don't need to remind you just how brittle castings are good luck
kennyf
March 2009