Is your coach a full length frame coach?? Some coaches are not and have a add-on frame that are not designed to hold weight and just designed to pull weight. Our 36' dolphin was that way. Hitch was there to "pull" a toad and not there to support tongue weight. Is your hitch rated for 10k#???
39+28=67. Plus probably some hitch length, so more likely 68-69ft overall. Does your state allow over 65ft length while towing??
2018 Vilano 375FL
2017 F-350 CC DRW 6.7