Just my two cents worth, but I think if I was building on that chassis, I'd leave the tongue long for a few big reasons. First, the long tongue will make backing easier because the trailer will be less flighty in reverse, and respond more smoothly. The longer tongue will allow you to back at sharper angles for more maneuverability, without having to worry about your carefully finished plywood hitting the tow vehicle. You will be able to more clearly see where the trailer is going in reverse because the longer tongue will hold it farther away and out of blind spots. The long tongue can be valuable space allowing room for an impressive tongue box to hold batteries, extra gear, and whatever else. I think I'd have a trash receptacle box on that long tongue as well. Be a responsible camper and pack out your garbage without having it stink up your interior or your car. That tongue is useful space I wouldn't abandon.
Just my opinion though

The build looks great so far