private int findExplicitThisParameter() {
		for (int i = 0; i < parameters.size(); i++) {
			ParamInfo p = parameters.get(i);
			if (!p.isAutoParameter() && Function.THIS_PARAM_NAME.equals(p.getName()) &&
				(p.getDataType() instanceof Pointer)) {
				return i;
			}
		}
		return -1;
	}
Switch to custom storage and perform required transformations
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/function/editor/FunctionData.java