It sure looks the part John!

I would say it is plenty strong enough too but if the ground is compacted to any depth you might find it lacking somewhat in which case I suggest about half as many tines and slope them forwards somewhat.
I was a farm boy many years ago and of course we had various types of harrows and in certain conditions it was necessary to weight the harrows or they just bounced along on the surface, but I think a quad bike would not have the traction to handle that.
About the worst thing I can imagine happening if you hit something solid (like what

?) would one or two of those tines bend, in which case you will get a piece of pipe and bend it back!
Great project.
