I would ask the question direct to Yalta, they should be able to tell you if they are able to withstand the load.
I would have thought it would have had the ski/tie down loops fitted through the transom as standard?? If not then I would be more inclined to fit them if tubing was going to be a regular use for the boat.
Just remember to whack a transom bridle on too as that will distribute the weight evenly rather than just attaching to a single point.
Cheers
Scott