I've been using a shoot-thru transducer for my Garmin 545s for a couple of seasons now and sensitivity seems fine. I placed the ducer a few inches off the centerline but don't know the hull thickness of a Pearson 28-2 at that spot. I didn't give hull thickness a thought, but do make sure your hull is solid and not cored--that's a show stopper.
2000 Beneteau 331
Northern Chesapeake Bay
Ambition is a poor excuse for not having enough sense to be lazy ~ Steven Wright