No doubt, but the lume is - like nearly every rep - a little thin ... why not make it better? And the price of a gen dial is not much higher than reluming ...
The mounting of your 21J movement is the problem. The Gen dial is set for ETA.
Start with a UPO w/ ETA clone if this is a project you want to proceed with.
This is my advice.
I'm not a tech guy. I'm sure there is more written about this same issue on the board.