Your boat is a Mast head rigged boat. The "I" dimension is 50.02 ft 15.25 meters. This puts the length of your mast at approximately 50 ft. Say 51ft to be conservative. How much free board (distance from the water to the deck) say 4 ft. You can get a tape and measure it standing on your dock.
Now I suspect you have a 3ft wire VHF antenna on the mast head. Maybe you don't. I would add 3ft to cover what is often called a "Bridge feeler/sensor".
Your up to about 58ft at this point. If you want to be conservative, Avoid bridge heights of less than 60 ft. If you must run up a river under a bridge, be sure that it is at low tide (check first if there is a channel that will let you navigate up the river with your 6.3ft draft). If your a little unsure, approach the fixed bridge dead slow and check the clearance with the "Bridge feeler/sensor".