[flashdance]

Oh, I see what you mean now! The block propagation delay that larger/faster blocks would cause could allow attackers to double spend with less than 50% of the network because the blocks of honest miners will be occasionally orphaned while your secret chain won't. The longer the delay... the more orphans, and the bigger advantage you have. Is that the effect that you are describing?

If you're interested in how big the delay is you can check this out, it's cited to the paper you linked me and I found it helpful.

http://ieeexplore.ieee.org/xpls/icp.jsp?arnumber=6688704