You're not giving us a lot of information here. Knowing the
rda would have been good and the wire gauge would help too for the hole size needed.
Having said that, sure you could drill the post hole bigger, if there is enough room to do it without making it too weak at the diameter you need. I would use a drill press for that and put the
rda in a vise to keep my fingers safe.
As for alternatives, can you use a screw head to trap the wires under? You could get a RDA with bigger post holes. Or buy a Trident, it has slots in the posts so it would work stock.
Can't think of anything else.
Vape safe