mounting Elliptical grab rails from taco marine

[bigbad 4cyl x2]

i need to mount my grab rails .they will be mounted directly to the fiberglass ,I'm wondering how i should through bolt them ,I'm feeling like if i bolt them directly to the fiberglass they might crack it as people yank on them . even with a backing plate. my thoughts are to use a piece of neoprene or maybe some 4200 under the mounting part . mount it loose, let the 4200 cure ,then crank down on it ,like a gasket ........any ideas how to mount grab rails ;http://tacomarine.com/item--Ellipti-Rail-Grab-Rails-3-4-x-1-1-2-Tube-Size--F27-1600+Series.html