Received mine last week, I too have the foam piece on the lower connection plate and I've not had any issues with it - however I have some much thinner foam tape that Is going to be replacing it when I fit the lock delete kit.
On an EMBN walkaround of Jonny Walkers Trek Rail he said he was using an 11 Speed Derailleur on a 12 speed setup as it is smaller than the equivalent 12 speed so is less prone to rock strikes. I really am not a fan of any derailleur (especially longer ones with big jockey wheels) so I'm trying...