Thornback Ray - width to weight?

Had a doubleshot of Ray last night, measuring 62cm and 50cm across the wings. Did not have a scales with me so would anyone have an idea about the kind of weight they would have been? Even though the larger ray was only 12cm longer across the wings it seemed a lot heavier. The fight was similar to landing a bag of cement. I gestimate 11 1/2 lbs and 6 lbs.

Link to page with formula for width to weight conversion .... for those mathamatically minded http://www.trjfas.org/pdf/issue_5_2/75_83.pdf

Have a couple of poor pics on my phone which I will try to upload later.

I had one Thornback Ray at 51cm/20 inch from tip to tip and it weighted 7.9lbs,you can gestimate a bit higher I think