I think the clustered index should be ( accounting_period ) or, if you prefer, ( accounting_period, prj_code ) rather than the other way around. I don't think phase_code needs to be in the clus key in this case, although I'm not against multi-column clus keys per se.
SQL DBA,SQL Server MVP(07, 08, 09) Prosecutor James Blackburn, in closing argument in the Fatal Vision murders trial:
If in the future, you should cry a tear, cry one for them [the murder victims]. If in the future, you should say a prayer, say one for them. And if in the future, you should light a candle, light one for them.