To get back to the OP's question, I tow with a V70 and it handles an egg like a dream. The aerodynamics are wonderful... I feel no wind resistance at all, nor is there anything noticeable wind-wise broadside. I've yet to pass (or be passed by) semi's on the freeway, so MMMV at that point.
What I learned through this process though, is that although Volvo recommends their factory hitch, the wiring on their factory hitch does not communicate well with NA trailers.
ORshepherd (member here) hitched up without difficulty -- they had an "OEM Volvo" hitch installed. (I don't know anything about this hitch, I just know that it was plug and play out of the box).
Everyone wonders why Volvo, with such a great towing background, is being so difficult about making towing easier in NA. To further illustrate this, I just took my V70 in today to get a transmission cooler installed. Volvo Steve reported that VOLVO NO LONGER MAKES A TRANNY COOLER FOR THE V70!
He's installing an after market cooler, but is unhappy he'll have to do things to the undercarriage to make it fit, whereas a Volvo cooler would have fit right in.
Regarding tongue weight
, the V70 is limited to 165 pounds, which is more than doable with a 13' egg. When we hitched up, the rear end of the car barely moved... it held up under the hitch weight