you did put something underneath that plate that seals off the 'spare-wheel-tyre-removed-round-thingy' didn't you?

The 'spare-wheel-cup' gives the rear (some/alot) of stiffness,. and it's attached to the rear panel, and mid-section traverse. But more important: Without any further strengthening, in case off a crash with a rear-impact (pole, car, tree) in the rear.. you won't believe how easy the rear will bend inward.

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