I can not measure my T Top at this time due to being in GTMO for business. I would say 4' X 6'. I wish I had my boat, the rentals leave something to be desired. I have never had a problem casting or the top getting in the way. I totally agree with the previous posters comments on curtains. The other benefits I see are a great mounting spot on the top rail for my planer board reels. I have the electronics box mounted underneath the top and have a FM/Sirius radio and VHF mounted up and out of the way. Rod holders (6) welded to the rear top bar for more storage. Install a "T Bag" and free up the space you currently are using for storing life vests. Another thing I did was mount a couple quick release clips on either side and have a boat hook and gaff mounted underneath the top up and out of the way. The basic boat design is pretty limited for storage and the addition of the top really added to the fishability and comfort.
Rick