btw I meant to put this with my last post, but remembered after I hit the submit buttor. anyway in response to the roughness thing, I believe it has to do with the banking. more specifically with the transition between bankings. if a coaster quickly switches from a right turn to a left turn then I experience head banging. example: Iron Wolf. great layout, but quite a bit of roughness for a B&M. it's fairly compact, especially the back. and its only in the back that I've had problems. now look at B:TR. the space between the helix and that turn is quite long. I experience no head banging until I hit the flat spins. again, there isn't much room to slowly roll into them. the other B&M's I've ridden have been ultra smooth. they've also been the larger of B&M's coasters. B&M allow the speed of the train to determine the size of the element instead of allowing the size of the element to determine the speed as other companies do (i.e. Arrow. Shockwave at SFGAm has its first loop elevated it slow the train down unlike B&M who make the larger elements like on Kumba, among others)
