Going from a Williams FP-Hawken Peep to a Soule type

I have several T/C Renegades with a Williams FP-Hawken peeps on the tang. I want to take one off and replace it with a Soule type. Probably a Lee shaver, but not certain at this point. Does that mean another hole must be drilled in the tang?

What I fear is every time I change the rear tang sight, I have to add another hole in it. Is this true and if so, how can I avoid it?
I haven't found any standardization among manufactures. I hope there is, but I have not seen it.

If I have a 57SML and go to a FP-Hawken or vice versa, does that mean another set of holes in the tang?

Thanks in advance