We have never been asked to weigh and we pass scales often in our travels and we live here. I think you have been miss led. US 20 and SR 120 are both decent roads straight across the top of the state if you don't want to use the toll road (2 axle trailers get charged commercial rates no matter how hard you argue). They are mostly 2 lane with cows and corn to look at. US 20 is being built up to 4 lane divided around Bristol to the west of South Bend so it travel faster there. I really doubt you will have any trouble on these roads.