Self-leveling suspension for towing?

[ChuckVT83]

X5world and bimmerfest forum have lots of happy X5 owners that tow, but in my searches I didn't see any comments as to whether the self-leveling suspension is needed for medium duty towing. Normally, I'd think it would be necessary, but I wanted to double check. What do you all think?

I am looking at a 2001 X5 3.0 automatic and need to tow a 20' bowrider boat that weighs 3500-3900 lbs depending on gas in the tank, gear, etc. This particularl X5 does not have the towing package, but I can add that at the dealer (I read the warnings about using after-market). This X5 also does not have the self-leveling suspension, hence, my question in this post.

TIA.

Chuck

P.S. The X5 would replace my 2001 A6 4.2. I currently tow with an 2005 Honda Pilot - the engine/tranny are great for towing, but the rear suspension sags considerably.