A pig touring with a boat anchor for motor makes that not a problem. I see that happening with a trailer longet than 24', or an over loaded trailer, poorly balanced trailer, or a trailer with a burnt bearing, and bad tires...and an accident. There are regulars at the ring who use their M5T's and 540iT's to tow their EVO 3's to the track all the time. I just can't see it being a problem in Adrian's situation. If you are really worried, call Zaraska in Canada for support. He tow's his M5's with a 91 750iL all over the damned country.

recap:
You have an oem towing setup
You have a 4.0 6 speed (enough engine, and your nose will tell you if your clutch is slipping unlike a slushbox which you could damage w/o knowing it.
You have an SLS/LAD leveling system in perfect working order
You have headlight adjusters for night driving
You are only towing an M3 which is lighter than M5's or E65's which Zaraska tows with his 525iT 5 speed conversion.

There is no rumpus here unless you have a 3/4 ton pickup in which case, which is more comfortable for the roadtrip.

end of story