You might be better/easier with just a Nylock nut, probably easier to get and saves the need for a split pin and so on. Given most things have nylocks nowodays they may be cheaper now, not sure but at one time I was quite big on replacing all castelated nuts with nylocks, then you start to see teh downsides (mainly if you have to heat them to remove) and now I find castelated quite quaint and actually pretty good.