I got that intake, too. I couldn't figure out why the hole was so small so I clamped it in my machinists vice and drilled the hole out a bunch, I'll have it off later and I'll up-date this but it's like 13/16th's of an inch now. It was the same as the stock ones, just over half an inch(I'll up-date that, too) I had to open the port a wee bit too.
I also radius'd the edges and removed the machining marks. I have read of billet intakes breaking. When aluminum breaks it's often from what are called stress risers, sharp edges where a crack can form. Removing them removes the stress point. Even though the part is slightly lighter it is actually able to handle the vibrations that cause the cracks from hammering up and down on the end of a barely supported tube. If there's room spacing the carb from the intake with a plastic or rubber tube adds shock absorption where there is none. Most of the weight on my intake and carb is being held by zip-ties around the plastic tube and tied to the seat post.