Soon to push the button on a dropper, but can’t decide whether to get a 27.2 (ruling out a Reverb) so I can use it on both bikes ( HT 27.2, FS 30.9) or just go with the 30.9 on the FS, which is probably where I’d use it most.

Any problems with shims?
Too much faff to switch?

Can’t afford two droppers….

Some suggest not using shims, if you are get long ones.

Just get a big bag of cable ties and have the cutters handy 🙂 Probably try and mark the position for both bikes too.

Or just get one for the FS and save a bit more.

Swapping’s no real faff- you could use reusable cable ties to save waste. Only really means undoing one more bolt (sometimes two)