I'd be especially careful in shallow channels- I have one in my sailing area- its only about 40" wide and the motorboats go thru it way to fast with the stabilizer loaded ( to keep the drinks from spilling) - I have 3-10 draft and at risk of bottoming out in the trough these boat make- (its a narrow and no wake zone...dahhh). I have to time momentary gunning of my 2 banger to keep my boat relatively level and not "jackknifing" on my rudder in the trough as these inconsiderate types blow past in either direction.
It sounds like your rudder was changed out by PO. IIRC on my 28.5, the rudder is only an inch or 2 shorter than the keel depth.