checking navigational attri check box for fully loaded infocube, will harm in any way??

Dear experts,

i have got to display data for material group wise in bex report(report built on cube ) . we have data for 0material in INFOCUBE and have material group as navigational attribute .but navigational attribute's check box not checked .

Q1:if i check it now without dropping data from cube ,will my cube get corrupt in any way ??

Q2:will materialgroup reflects properly in report ???

thanks in advance ,

useful answers will be rewarded with full points ,

regards,

Hari.