Can we retroactively amend during amendment period

[R. Butler]

I've asked this under 401(k) board, but its more of a document question. so I will ask it here.

I've got a Parent/subsidiary controlled group. Two employers A & B; each maintain its own Plan. B can't pass coverage on its own, so we aggregate. Now here is my problem, since I aggregate for coverage, I've got to aggregate for ADP/ACP. A uses current year testing; B uses prior year testing. Can B retroactively be amended to use current year?

B has already amended for GUST, but I am hoping that since we are still within the remedial amendment period that its permissable to do that retroactivce amendment.