Yes, the tower muffler is pretty big, but it just clears the tunnel cut-out on the bottom side. I actually thought the OS 91 had a longer muffler, which was one reason I didn't spring for that engine. Also, this plane can be flown from anything from a 46-91 2-stroke, so I figured the tower 75 was right in the middle. I think the vert with this plane is very good. Obvioulsy it is not unlimited, but it gets up there pretty quick with a 13x6 zinger. I got rid of the remote needle on the tower engine and it is running great. That was another reason I didn't go for the OS- can't get rid of the remote needle[:@] I don't hover close to the ground yet, so I can't commment on the tower's ability to pull it out of a hover, but I bet it could do it, but not as strongly as the OS.