Hybrid Crop...

Hello,



I am doing shoot where I give the clients CDs and do not know how they are going to print the final image.



Since my 5D is 8x12, the 8x10 crop does the most damage.



Does anybody know if I can overlay an 8x10 area while I am cropping for 8x12?



This would be a shadow type border inside the 8x12 crop area to see if I was still safe for 8x10 printout.



The CD thing is very popular and is the future of distribution for a lot of photography.



It would be nice to see Lightroom address this trend.



Thanks