Well to be honest with you - I read this post earlier, but had no idea of what you were suggesting. After seeing it I have to wonder if only attaching to two bolts is really adequate - seems if it were me I would at least tie into two more at a bare minimum. Next I would consider adding another piece of plate - attached so it leans down - like a "normal" bellhousing - in an attempt to contain schrapnel from exiting rearward. As it is now I'd be afraid that any explosion wouldn't be contained - instead it'd tend to just "unfold" your plate. But on the other hand - what the hell do I know!!!!
Every scattershield I've ever seen covered the entire bellhousing. If you clutch explodes on your setup isn't going to handle it IMHO. Edit: there are some pics on here of explostion and seems all of them exploded back and up into the firewall and floorboard area. You may want to check out those pics so you get an idea of what area needs to be covered in order to contain the explosion.
Can you add to it? Add some plates that comform to the bellhousing area. I just didn't want you to have a false sense of security about this. If it is a big enough concern of your's to build the shield, then you need to do it 100% for full protection. Good luck with it.