Hi Eric

I am looking at getting the P5D, but unsure which size will fit me, so your help would be greatly appreciated.

I'm currently on a 2017 P2 size 54 and have gotten a pretty good fit from a bikefitter, but I'm not sure the fit measurements are the same as the ones you are using. The data from my bikefit sheet is:

Reach: 490 (from middle saddle to middle pads, I think).
Stack: -70 (drop from middle saddle to middle pads)
Pad Z: 240

Do I need to take some new measurements?

Thanks,
Soren