You should be able to ESTIMATE the change in tongue weight by summing the moments around the trailer axle with this formula, where:
N= weight of new load on the back of the bumper = 230 lbs
T= change in the tongue weight (reduction)lbs
B= distance from center of your wheels to the center of the 230 lbs new load in back
F= distance from center of your wheels to the tongue
Then: T=230*B/F
This formula works if this is 230 lbs of NEW load for the trailer. IF you are taking 230 lbs of existing stuff out of the trailer and just moving it to the back, then there is more calculation involved.
IF you have a single trailer axle I think you will see some change at the tongue - but at 22 feet and 6500 lbs this MUST(?) be a double axle. If you have a double trailer axle, the calculation gets messy and the impact at the tongue is probably less because the pivot point at the wheels is almost 5 feet long and provides resistance to the teeter-toter effect of the weight change.
No extra charge: you will be adding load on your trailer wheels equal to 230-T
Change to WD hitch probably depends on number of axles, whether the WD hitch is adjusted correctly before the new load is added, and whether the current adjustment is light or aggressive. We pull a 7600 lb trailer with a '13 Tundra and I have to set my Equalizer hitch very aggressive to push the front of the truck down due to the length(double cab). If yours pulls OK now, I would be shocked if you had to adjust it for 230 lbs on the back.
