Class VII Testing

I have a class VII Transit and a couple of weeks ago I removed the rear brake drums to check the brakes for servicing. I changed the shoes and cylinders along with a brake hard wear kit and one new adjuster that somebody had damage due to incorrect assemble at some previous time. I drove the van home and did not notice any issues with the brakes, then a couple of weeks later, not having used the van I got some new brake drums, after fitting the drums the brakes have excessive brake fluctuation and you can feel the high spots while turning the drums. I suspect that the new drums are oval and I am in the process of contacting the suppliers to resolve this. Driving the van the brake pedal is up and down like a sea saw, but my question to you class VII testers is;

Given the axle weight in the rollers, what sort of figures do you normally observe as brake drag a for an unladen van of this size!! 

Should there be any?

Thanks