Are the bunks sitting directly under the stringers of the boat? Typically there is a chine in the hull at the stringer line, you should set the bunks so they ride along side or directly under the chines. I've got a heavy boat with bunk trailer--works great but, I spent an entire day at the boat ramp adjusting the trailer to fit the boat.
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Have you ever listened to someone for a while and wondered..."who ties your shoelaces for you?"