merge replication - adding indexes to metadata tables

Hi All,

What is the general consensus on adding additional indexes to replication metadata tables ?

If I use the dm_db_missing_index_group_stats DMV, amongst other things it (strongly) suggests adding an index to the following

[dbo].[MSmerge_identity_range], columns [artid], [is_pub_range]  nb this table has 350k rows

I'm aware that this could be a two-edged sword -  has anyone any advice on whether I should do this ?

Or are the metadata tables considered sacrosanct and for MS only; would this impact any support from them.

This is for merge rep, publisher at SQL 2014, ~500 subscribers on sqlexpress.

Thanks

BTTF