Wouter,
Have you come across any ways to "seal" a T fitting in a mast?

The Marstrom carbon Tornado mast uses a T for the main hounds. Although they've used expanded foam at the opening and also just above the lower diamond rod fittings, the mast will still take on water and turtle the boat.
First 2 times I capsized with the new carbon stick, I was surprised she just stayed on her side for many minutes, even in 25+ knots wind. The 3rd time I capsized, she went down within 90 seconds in only 15 kts wind. I suspect the foam seals had opened up some. Once we had her righted, you could see some water coming down & out of the mast from above. After about 1 min., this trickle turned into a huge gusher...presumably as the inner foam "dam" broke through.

I'm thinking the fill the upper T fitting cavity in the foam with body filler and then grind it out enough to place the T back in. Or, just body fill the whole T fitting in place and use silicone sealant to allow some movement of the fitting. Ultimate solution would be to replace the T with a standard flange, but I don't want to get too far from Marstrom's concept at this time (re-inforcing of the area would likely be needed and class rules are fairly strict on the mast measurements & tip weights etc).