If you file expert report, in proper form, before suit is filed, you do not comply with the statute which says to file the report after suit is filed.  You loose.  St. Luke's Episcopal Hospital v. Poland, 288 S.W.2d 38 (Tex.App. --- Houston [1st Dist.] 2009, ).

Contra, in principle, Rule 306c which deems as timely, motion for new trial with is filed too soon.

Real rule of decision is to deprive relief for as many plaintiffs as possible.