It might be possible, but it is completely illegal and if you have water cops or USCG anywhere in your area, you will get busted in a heart beat...
The law states that anyone towing a skier, tuber, etc... Must have a dedicated spotter onboard the boat (Ski) at all times. In most states the spotter has to be at least 16 years old... The boat doing the towing needs to have sufficient capacity for the driver, the spotter and anyone being towed...
That means you have to have room for everyone and if you have two people on the tube you better have a 4 place boat (or Seadoo LRV)... Last time I checked the SXR was rated for 1 person @ like 300 lbs max... So even if you put some one on the hood as a spotter I don't think you can get a third on there and get under the weight capacity...
Not to mention it is not safe at all... What will you do in the event of an emergency?... How would you get an injured or unconscious person to shore?