Two bikes locked together should also stand up better than one bike, even with a stand, especially on grass.
The area set aside for bike parking should be big enough that the bikes can be parked in rows, so early comers can still get their bikes out. If people are a little disciplined about it, we should avoid the 'huge tangled heap' scenario that I know people are worried about
The reason behind all this was that the police were concerned about the capacity of the area immediately outside Parliament if everyone hung onto their bike, so they were talking about limiting numbers, which obviously would limit the impact of PoP. It seemed that a marshalled parking area was the lesser of two evils. I hope we can all make it work out