I haven't actually measured mine yet, but I'm curious: I looked down one time, and noticed that the chain was about parallel to the top tube somewhere inbetween 4th and 5th on my freewheel, while on the small chainring. Is that an optical illusion?

[When I took apart the BB, I found a Sakae MTBS411 crank axle. I measured 125mm rear dropout, and I run a 6 speed SIS freewheel.]