Nice report! The reason Millennium Force may have seemed slower in the station isn't so much riders being too heavy to get in the seats, but rather a new dispatch program they have been running now for two seasons. If they are running three trains, they do not dispatch a train until the one on the track has fully completed the circuit. In the past, a train would dispatch as another flew by the station. It isn't a fault of any employee or ACE member who has put on a few pounds, but rather a new operating policy. I don't know if it had anything to do with the accident on RoS a few years ago, but the dispatch intervals did seem to change around this time.
As for Mantis? I went to CP a few weeks ago, and Mantis seemed to be running fine. The only reason I don't ride it more is because the line moves slower than any other major ride there. Very little trim and head banging made for an excellent ride! It isn't as smooth as some other B&Ms, but it is still pretty smooth while packing a wallop at the same time. When it is untrimmed, no B&M I've ridden to date has so many packed positive g's. The ride isn't everybody's cup of Joe, but luckily you were at one of the few parks where you can be picky about the coaster styles and still have a great time. I'll be looking forward to your KW TR .