I run with John Howards design as well. A key to his design is that is also incorporates the use of keel rollers as the actual load points. The tailor fit bunks help with on and off of a nicely waxed boat. These bunks should be equal if not just a hair less in height to allow the keel rollers to engage the load. Yes, bearing on outer bunks only will flex the foam blocks free over time. My '79 boat already has some "oil drum" , but it was a pre existing condition. Guess what my next project is .