The only thing you didnt do when you ground on them..
you should have used some finer tootsie rolls to
eliminate the rough stress risers and radius it.. you
most likely wont have any issues with low spring pressure
and low rpm as you are... I've ground on rockers also
for clearance with mucher higher spring pressures
and a couple thousand more rpm and they still havent
failed... just remember any sharp edge is a break point