Oregon 126 between Eugene and Florence on the coast is an excellent road. No concern for RVs. Thousands of them make the trek back and forth between I-5 and Highway 101 every year. I do recommend you take the Randy Pape Beltline highway (MP 195) off Interstate 5 at the north end of Eugene to get over to Highway 126 as it bypasses all of downtown Eugene. Highway 126 is a beautiful drive to Florence, on the coast. I must point out, though, that the Highway 138/38 route taking you from I-5 to Reedsport on the coast will save you about 45 minutes of drive time, if you are coming from the south, and if time is of concern to you.