That's not a bad idea, IMO. Sometimes you gotta do with what ya got.
And you already know it is not the safest thing to do (no lecture from me).
If me, I would cut a prop to stick under the bucket, just in case. But I see you have already planned for an 'event' where the bucket might drop. Just that a potential bump of the hyd. levers by you or someone else may cause some anxiety attacks, when the plywood doesn't protect the new siding.
Looks like you are about done, so good luck with the finishing in a timely and safe manner.
Let us know if you need on a prayer chain /forums/images/graemlins/grin.gif