I'd like to move my Brooks saddle back and forth easily from one of my bikes to the other, but they have different sized seat posts. One is 25.0 and the other is 26.5. I could shim the narrower post with sheet aluminum, but I wonder if anyone has a better, more elegant solution. Some day I might buy a second Brooks, but the budget won't stand it right now (I just bought a B-17N S for my wife's bike).

Unclamping the posts from the seat rails is not an option for quick changes.

Sheldon Brown says seat tubes can be reamed to take larger posts, but 1.5 mm seems like a dangerous amount to take off a seat tube.