M_Boats: trailering M15 while battery is strapped onto boat bottom

this may be a dumb question, but where else to ask but here... am contemplating trailering my 2009 M15, with two 12 volt car type batteries (about 20 pounds each), strapped into their compartments, under the cabin storage panel, placed onto the boat bottom it'll be mostly highway travel, but i don't know how strong the boat bottom is, and my first thought is that to do so is a dumb idea and may cause damage to the boat bottom, and its just better to have the batteries in the towing vehicle thanks for any thoughts on the matter! - brad