I might try some of these things and apply them in Qimage. Qimage is a good fit for my business at the moment, if I can get everything to work...
I found that LR printing was completely broken. It just would not print successfully to my P6000. I'm talking prints that would start and then just stop half way through. It was very strange behavior so I abandoned it.
One of the problems is that much of my printing is based on my hard headed adherence to standard paper size. I think this benefits my customers because framing is such a challenge when you offer 12x18, 13x19, 17x22 or other odd digital printing sizes. Plus I'm printing almost exclusively from film scans, so I see a lot of different image ratios. If someone is shooting a Rolleiflex, and orders an 8x10, well that generally means I'm making a 7x7" printed image floated into an 8x10 canvas and bottom weighted with a 2" border on top. Or similarly a 4x5 image on 11x14 must be right sized in the canvas, or cropped to fit... Of course I do any size on request but these are my standard menu choices.
If anyone at Qimage is listening, I'd kill for drop in templates like this. I just want to print as if I was printing in a darkroom. You mask off areas of the paper so there are the proper edges and it fits within your planned mat.