1) Did you try using manual alignment tool in photomerge workflow? I believe you can use them to fix the alignment issues in your photos unless you are facing large scale alignment issues
2) Though nothing has been documented about the size images in Photomerge workflow, I believe working between 11-12 MP should give the best result for Photomerge.
Another fact that I am unable to understand is that since Photomerge workflows have been created using actions, they shouldn't be affected by the size of the image used
Thanks for the help. These photos have extremely small misalignments and usually automatically align well after reducing the size.
I tried the manual alignment tool and it is very tedious as you have to do both manual blending and manual alignment. There doesn't seem to be a way to automatically blend and manually align.
Of course if the automatic alignment feature actually worked I wouldn't have this problem. I can see spending the time for one or two sets of photos but I took dozens of sets on this latest shoot and can't bear the thought of manually adjusting all these photos.
I'm now left with having to batch reduce all my photos in this group to something that will work. I was just hoping to get some guidance on some "known" maximum size for this feature. I will try your 11-12 MP suggestion and see where it gets me.