On one previous boat I had a furling mast with a track that was for a storm tri-sail only. The track did not go to the top. This may not be the case on your mast, so excuse this if I'm bringing up the obvious.
The other factor was the track was on one side of the slot. Don't know if that's true as well, but a large mast section might do some interesting things to air flow. Probably doesn't matter when it's blowing 50 kts and the trisail is up, but might matter in lighter winds.