OP's :S... not sure why I ASSUMED you had a 5er as this post is in the TT section. YES 150 lbs on the back of a TT can take enough tongue weight off that the handling will suffer. The closest I ever came to loosing a trailer was when I loaded 200 lbs of parts in the back of a single axle Airstream (many years ago) and at 45 mph it almost took me to the scene of the accident. Back then you had to manually put on the trailer brakes which I did as I hit the gas. This stopped the sway an and then I was able to get off the gas and get stopped. Moved 100 lbs to the front and ever since I make sure I have plenty of tongue weight.
It's absurd how many trailer undercarriages are so close to the loaded weight for a savings of a couple hundred dollars.
