Yup I use them in Eric Jr, well, I did up until today when I replaced them with an XL.

Didn't have any issues with different speeds reversing and in forward drive, didn't notice anything at all. I just swapped them out as they're only rated to 12v (although I used them on 14.4 with no issue) and wanted to be able to run something at 19.2v and keep both my feathers using the same battery sets.