Thanks for all the great suggestions everyone.
Woodcraft didn't have one of those clamps in stock so that idea is out. They also said end grain to end grain won't be that strong of a joint. Looks like I kind of messed up by doing the profiles first.
I've wanted to do splines for a while now but time is running out and I don't want to make a learning mistake on this project! The trim turned out really nice and my luck I would make a mistake and have to start all over. So I think splines are out.
I did pick up some of these clamping "blocks", http://www.woodcraft.com/Product/208...ng-Blocks.aspx
. I didn't think they would really work here since the profiles are already cut but they did look handy so I picked them up!
I also have some of these corner clamps I bought a while ago, http://www.woodcraft.com/Product/200...ner-Clamp.aspx
. I don't think they are the best for what I want to do but I think I'm going to use them.
I picked up some corrugated nails from woodcraft also. Didn't really want to use them but they should provide more strength then just a glued end grain joint. I'm hoping between them and the glue it will hold up. If not I guess I will have to build a better frame down the road and just replace this one.
One last thing, would dowels work here? As in drill into each miter end grain and use a dowel? I have a nice dowel jog and would be easy to do. Just don't have much experience using dowels. Something like this,