Perimeter of flat pattern

Attempting to measure total distance to laser cut this piece of sheetmetal.   Followed directions in another post here about unbending and then creating a cross section thru the thickness and then a datum curve thru that section.  Upon creation of the datum curve it wants to bend back the form so I can't get the curve to go thru the flat.  It's too tedious to measure each length of entity to burn picking them individually.

I can't be the first one to have this issue.  I'm in Creo 4 if it matters.

Thanks