I tried to put one on a mates bike yesterday, Pacestar 2.6.
Had to take it to the bike shop in the end use one of those Shwalbe air canister things. We put a 2.35 magic mary on the front which went straight up with my track pump.
To me it looked quite similar in size to the MM. I was expecting it to look a lot bigger. His rims are 25mm internal.