rb26stagea here: I'm on a mate's computer... I have removed the roof bars from my car, and I can tell you they are extremely solid: they are steel underneath the plastic coating - you should have no issues with a small inflatable on them. I estimate they weigh at least 15kg each. worst case, if you were to bend them (VERY unlikely), I have a set sitting here that I am willing to part with. That said, you should not have any issues at all...