A 39' 5er will be considerably longer due to the truck needed to pull it. That 39' will turn into 50 - 55 feet.
And as mentioned, driving a dp is totally different than driving a truck pulling a large trailer. Completely different characteristics. If you've had experience pulling a large trailer before, then you shouldn't have a problem....if not, then you will have a learning curve to attend to. Only commonality between them would be both are large vehicles that require a lot of space to travel. Driving a dp will provide you with the experience needed....no learning curve there. But turning, backing, and just going down the highway will be different.
Ron, Sandie and Lilly
2013 Tiffin Phaeton 42LH 400 ISL | 2011 GMC Terrain SLT-2
Roadmaster All Terrain | US Gear Unified Brake System | Pressure Pro