hyundaitech or anyone: towing Elantra behind an RV?

Not really a tech question but....

I bought an '07 Elantra GLS with the 5 speed manual with the idea of towing
it 4 wheels down behind my RV. I had read some RV articles saying that the
Elantras could be towed this way without damage to the car or the warranty,
and a mechanic who I trust (my brother in law) says 90% of manual
transmission cars can be towed this way without modifications or damage.

The thing I'm a little puzzled about is the '07 Elantra owner's guide
doesn't mention this and in fact urges caution when towing an auto tyranny 4
wheels down (don't exceed 25 MPH), but doesn't say anything about a manual
transmission.

Haven't been able to find any other info except for what I previously
mentioned. I have posted on some RV forums and gotten a mixed response.

Any idea if I can tow this car 4 wheels down without damage and if I do, any
idea if it will void my warranty? (I'm going guess yes since it's not
authorized in the owner's manual). Some car makers will allow you to tow
their manual transmission cars this way (Nissan, Saturn, Toyota to name a
few) without voiding the warranty on the car. Of course the dealership says
to go for it, but for various reasons I don't trust them all that much.

If worse comes to worse, I'll hook the new Elantra up to a car dolly for
this purpose but would rather avoid the extra 600 - 800 lbs of tow weight.

A.