Not sure where the 29' measure comes from on the T mast. I measure from the top to the bottom of the mast section (not including the base) of a marstrom untapered aluminum section, 30'- 10 3/4". Now the luff of the sail may be around 29' but mast is about 31'.

The T chute and the N-20 chute may be the same area but the N-20 is a class sail built by one manufacturer. The T sail can be made flat or full and by anyone as long as it measures in.