It depends. I say YES, its okay. I used to do an 8x10 print, but do a overmat with a 1/2inch border around the print edge. So, it makes the window 9x11. I would set the print up 1/2" also. I think this looks fine, but if you are window matting INTO the image itself...I think it gets sorta small. Remember thought, big matting is always better then small.
To save money and for other reasons, I use 14x17 for all my prints 8x10 and smaller now.