I had a bike fit recently and was wondering about transferring the fit data to my other bike.

I realise that some things such as bar height are going to depend on the bike's geometry and I'm not going to replicate an endurance bike fit on a race bike, but I was wondering about saddle set-back. I've been told that this is a "fixed value" for a given rider, once they've worked it out via their preferred method (KOPS, balance test, gut feeling...). Much like saddle height that is determined by your cycling inseam (at least on road bikes). Reach variations should be done only by changing stem length & angle, or getting a frame with a different top-tube length.

It this a good rule, even if you change between bike sizes or geometries? I'm assuming that the set-back can be measured from some agreed reference point on the saddle (e.g. sit-bone position).

Thanks!