I played around with my mill gap and ended up leaving it at .030", with my setup (Recirculating Herms) I saw no improvements beyond this setting. I do mill at a low speed however just because the mill will tear the husks up if I speed it up to much. I have had no problems either way except if i open my valves to fast during recirculation I compact the grain bed, so I allow the hose to fill then close my valve and then open it wide slowly.
Just some background in my experience however the purpose of my post is to share information from New Brewing Lager Beer by Greg Noonan.
Coarsely ground malt does not yield the extract that it should. Heavy gummy insufficiently modified starch particles interfere with mash filtering. In general it it better to crush malt too finely (at the risk of a stuck mash) taking extra care doughing in, and sparking that to not mill finely enough. Balled flour is inaccessible to enzymes during the mash and can result in unconverted starch, some of which can wash into your sparge and leave irreversible haze in the beer.
These are guidelines we followed before reading the book, based on experiences and experiments (some of which were trial and error). I had always feared of astringency and the fact that other brewers suggesting a lower efficiency is better to prevent bad things from happening. Although i never experienced those things I thought i was lucky, reading this book relived my fears and validated what I was doing. My dad is my brewing partner and our method has been successful for us, one will slowly introduce to grain to the tun while the other stirs it in to ensure no dough balls. We usually get a full conversion based on beer smith calculations, we don't do iodine tests. Our last brew calculated to a 99.99% mash efficiency according to beer smith(usually above 95%) and our setup yields a 82-85% total efficiency. I also should add that our beers don't exhibit any astringency or off flavors related to the crush/mash.
Slightly off topic from the original question posted (will x2 crush help) but I thought this information would be helpful to the overall theme.