Yes
What i did was get some rubber washers at TrueValue and put them around my bolts, to stop any leaks. Also though on my pivot bolt, and on the trunk of the keel I made what I call a trunk saddle to take the weight off the fiberglass. I made it out of 1/8th in aluminum and ran my pivot bolt through it. It sets over the whole trunk like a saddle. It is in the archives or I could put another pic of it up here. I also rebuilt around the pivot bolt hole the fiberglass making it thicker for more strength! As to sailing without the keel locked down, in fresh water that is fine, with the keel resting against it, but if you go to sea, I would definately lock the keel down! it is much rougher out there, than a lake! It depends of course on conditions! The rubber bumper your talking about, I am not sure about, I have a stop bolt, that prevents the keel from moving forward any further. Perhaps yours does have a rubber bumper. At any rate, both would do the same thing, and that is limit the keel movement! You could always put a bolt in, if your not sure!If you sail with the keel not locked down, you still have to have the lock bolt in place or water will come in! The keel will simply rest against the bolt! At sea if you ever had a roll over, and the keel wasnt locked down, well you could see the disaster!