Originally Posted by
tomtomtom123
My derailleur spec is 61-66 angle to the chainstay-BB axis. I have it at 66 degrees.
Using the same model for your bike might not give you the right angles that you need since you've got a smaller rim and possibly different seatpost angle.
I did some quick assessments last night and the space for having a mounting adapter above the derailleur is very tight in Brompton, tighter than in your Dahon, and the band of the adapter might interfere with the latch holding Brompton's rear triangle. While I only did an in situ angle measurement, it seems that, amazingly, my derailleur mounting point is now at about 65 degrees about the BB axis away from horizontal.
Given the amount of flexing and twisting I observed for the K-frame mount's finger on occasions, with the setup still surviving, I will look next into more improvised derailleur mounting, combining a hanger for carbon frames with hose clamps, but this will have to wait until after my trip. I do not like the flexing, but if the shifting can somehow tolerate it, so be it. After all, the cages both for the front and rear derailleurs on bikes undergo horrors and all that still functions.