I've been wrestling with this same question. After talking to dealers, handy fellers, etc I don't think it's a good idea. I do not have QA but will get a separate spear mount attachment vs attaching to the bucket.
It's tempting, but I've been convinced I'll ruin the bucket.
I'm sure you could do it, but you'd have to really make a strong bracket to spread the stress and protect the bucket. Plus, as noted, the spear gets really far out front of the bucket and away from the loader arms.
Let us know what you decide though.
Good luck.