Looks good. Will not come loose. I think that hole may be for radio antenna cable. Also, speaking of new roller bearing kit being cheaper than new ball bearings...... O'Reilly PN for wheel cylinders (no mess, no risk of screw up, lifetime warranty and kits have Chinese "rubber" same as O'Reilly's new cylinder).
WC13387 WC13388 $9 & $10= $19
Wheel cylinder kits $6 x 2= $12 or more and/or shipping
Maximum Delta $7

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn