There are almost never cars parked on our street (culdesac at the end of our street) and we cannot keep cars on the street anyways. I can use the driveway across the street if necessary, and I dont think I will have any issue with the mailboxes...my main concern was dragging the bottom
All that being said...the fifth will sit up higher I am guessing...more ground clearance in the back perhaps...and I can cut it much sharper than a trailer I would think (I have towed lots of big and small trailers and boats, but never a fifth wheel)