A little while ago an Article by Neil Erasmus in the very good Australian Wood Review (AWR) magazine, showed an ingenious method of reinforcing mitred corners. I can't find my copy but I'm sure this is the cabinet he used them on, please correct me if I've got any of that wrong!
You can see some of Neil and Pam's great work here http://erasmusdesigns.com/index.php/furniture-all
His method involved joining two Dominoes at right angled which allowed the splines to be inserted in line with each board. I'm sure he used finger joints but I dovetailed mine.
The four sides of my box were cut square and the dominoes cut at the maximum depth the machine would allow.
They were then mitred on the table saw. The twelve Domino joints took just under an hour to do. They were then trimmed to length leaving a small glue gap at the bottom of the mortise.
The splines were glued into the two opposite sides making sure they went in all the way and then the other two sides were glued on.
This meant everything could be glued up at 90 degrees instead of being pulled together with band clamps, so avoiding the struggle of stopping the parts slipping or opening at the corners. It went together like a dream and the corners all lined up perfectly. I'll be doing an article for F&C on this box in the coming months with a few other good tips as well.