Depends on the truck. I loaded some "green" red
oak 8x8 beams in a Toyota tacoma that were 10'. I was only going 1 mile. The weight was so ridiculous I went of a rise and completely lost steering for a second. The resulting bouncing periodically caused the steering to regain, lose, regain lose for about 100 yards. Enough to cause major pucker.
Obviously WAY overloaded. Cause a slight bow in the tailgate, surprised it wasn't worse actually.
My Chevy 2500HD? Wouldn't even give it a seconds thought even if I had a goldwing in there.
You could always turn a ramp upside down, like a U channel and as long as the front wheel is on the ramp should eliminate any worry even on a lightweight truck as the back of the bed will help distribute the load going over bumps.