Hi Glen,
 
Here is the info Tapas Das supplied on the forum. (see attachment). 
 
I'm a little concerned as I recall that I purchased metric fasteners to attach the rails to the HD and I didn't think any washers were required for a tight fit.
 
But, I'd have to dig into my i30 and I wouldn't be sure what screws I put in there anyhow just by looking at them. 
 
So, guess it is okay to post the attached info on your website - I'm cc'ing Tapas and he may comment on my concerns. Okay?
 
JerryS