There is always the Thule goal post. Puts a damper on towing though. Then I thought about modifying it to sit on the bumper. More $. Then I priced the roof rack. Even more $. You need to support the yak where it needs support. It is not about the length of over hang. I rest mine at the bulkhead on the stern and the bow falls near the opening on the cockpit. I find it gives ample support without distortion.
The foam blocks I bought especially made for resting a boat on. Picked them up at an outfitters store. They had the groove cut in them for a square bar already. I just made some relief cuts to fit them to my rack.