§6.1 In-script variants is proposing to disallow <chillu-n, virama, rra>. However, as per Unicode (Standard Version 11.0.0 §12.9 page 506 table 12-38) <chillu-n, virama, rra> is the prescribed sequence for the form {chillu-n base, rra below-base}. Because of this conflict with Unicode, the sequence <chillu-n, virama, rra> should not be disallowed.

Regards,

Cibu