I don't think there will be a correct (precise) answer here due to differences between trailers and their TVs.
With my previous bumper mount camper I used a WDH - which displaced the ball several inches back. However now, using a bed mounted hitch, the mounting point has moved forward - perhaps the 4 feet previously mentioned.
But the leading edge of my current 5th sits several feet (?) ahead of the mounting point.
2008 Jayco Eagle SuperLite 29.5
2014 F250 6.7 PSD 4X4, CC LB