I think this section of the proposed regs ius pretty relevant because I believe it must be followed to use the "in plan roth conversion" correction method? 1.414(v)-2(c)(3)(i).
(3) General correction requirements —(i) Practices and procedures. For a plan to be eligible to use either of the correction methods described under paragraph (c)(2) of this section with respect to an elective deferral that is a catch-up contribution because it exceeds a statutory limit described in § 1.414(v)-1(b)(1)(i), the plan sponsor or plan administrator must have in place practices and procedures designed to result in compliance with section 414(v)(7) at the time the elective deferral is made. As part of these practices and procedures, the plan must provide that the elective deferrals of a participant who is subject to the Roth catch-up requirement under paragraph (a)(2) of this section, but who has not made an affirmative election to make catch-up contributions as designated Roth contributions nor made designated Roth contributions equal to the applicable dollar catch-up limit earlier in a calendar year, are automatically treated as designated Roth contributions after the participant's pre-tax elective deferrals made during the calendar year equal the section 401(a)(30) limit on elective deferrals for the taxable year that begins in the calendar year. Similarly, the elective deferrals of such a participant who has not made an affirmative election to make catch-up contributions as designated Roth contributions nor made designated Roth contributions equal to the applicable dollar catch-up limit earlier in the limitation year must be automatically treated as designated Roth contributions after the participant's pre-tax elective deferrals result in the participant's annual additions for the limitation year exceeding the section 415(c) limit for the limitation year.