I need a trailer and looking to get an enclosed trailer to tow behind my 2004 e53 3.0. I don't have a tow package on this car and will have to settle for an aftermarket tow bar.

What specifications should I be looking for to be able to safely tow long distance without breaking the car? i.e. Is a 6x12 enclosed trailer too heavy for a 3.0? 6x10 safer? Single axle or dual axle?

Any recommendations and insights would be appreciated.

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2004 X5 3.0