Hammer. i think i had a similar problem. when you would load or unload, i could feel a hard bump when the bow was over the axels. *i have a float on style trailer, no rollers with tandem torsion axels. *when i first got the trailer, it was equiped with double 12" rollers on the first crossmember(from the tongue). *it loaded & unloaded great, but the keel hit the first axel. *i then installed the Y bracket. *the keel still hit. *then i installed the bunks and they work great. *i had the repair & glass about 24 inches of the keel, but now its been 3 years and no new dings. *i know you like photos so i tried.
the two original brackets
side & front shot of the new bunks
the "whiter " area is the part I had to re-glass & the carpet scraped off the paint.
hope it helps