OK, I´m back from holidays and I could do some more miles on the cat. I´m taching ok now, the tip that worked for me was to release the jib sheet late, after the boat has surpased the necessary angle to fill the jib at the new direction. I could set a hull flying, but with no more than two on board, with more weight and enough wind to raise a hull, the tip was too close to sink. It did once in fact, I could manage to avoid capsizing.
One of the hulls is filling with water, I couldn´t find where, I filled the hull with water to the top (I was a little nervous it could explode..), but didn´t find any leaking, so I suppose it is somewhere on the top, probably through the bolts or through the metal that holds the trampoline.
I missed one tip though, and I learned it too late: be careful when releasing the trap wire, particularly if you are on the back seat, it might go directly to your partners face.. (in this case my wife...)

Use a squirt bottle of soapy water on the hulls- on seams, holes, chips, or cracks INSIDE the daggerboard wells. Put on LITTLE pressure from the blower side of your wife's vacuum cleaner machine: Hold the hose in the open porthole, closing off the spaces with your hands until you feel some back pressure. Now squirt & rub & look for bubbles. Wives and kids love to do this: & your hands get really clean.

Do NOT use your wife's hair dryer because it will burn out almost instantly. I know this from experience and very angry wife. This is why I have several $1 garage-sale hair dryers covered with epoxy fingerprints- used to heat up my repair jobs. Remember epoxy comes off hands and parts well with cheap rubbing alcohol (70% or 90% isopropyl alcohol).