A more practical circuit for trimming the output V would look like this. The trim-pot is 10k and is in parallel with 100R, which largely mitigates the trim-pots large temperature co-efficient and the adjustment range can be reduced to the required +/- a few %.
Also, using exclusively, say, just for example, either 25ppm or 50ppm resistors in this circuit will not respectively automatically return an output drift of 50ppm or 100ppm. The actual drift contribution from the feedback network will be somewhat lower due to the fact that the resistors will drift by the same proportion if in the same thermal environment.