Personally I wouldn't have a trunk rack. I would (and did) go with a pakit rack. This allows you to haul stuff when you need it and not disturb the natural trunk lines especially if you have a spoiler.
mounted the kuryakyn rack and it was pretty easy. just remember the angle of the legs. and measure twice/drill once. the instructions said to drill through the inner trunk with the back 2 bolts. i didnt do this and it worked out great.
I set mine on masking tape, centered it by eye and also by measuring. Drew circles around the legs and drilled the center of the circles. I made huge aluminum washers (2") for the inside and outside on my 1200 and backed the washers with rubber inner tubes cut into 2" circles. I agree that luggage racks don't look particularly good, they are difficult to clean around, and they can subject the lid to stresses. But when you've got to get something home, they can save a trip with the four wheel vehicle.
I did mine like metal man. I eyeballed the entire thing and it worked out great however I took out the inner liner of the lid first. I love mine when I take trips. I have strapped everything from helmets to chairs onto mine... never have I had any problems with cracks or such.
Get a friend to help you. Four hands and eyes will be helpful. Double plus on the masking tape. Use a new or just sharpened drill bit the exact
size of the bolts. I called Kury' for tips when I did mine and they told me
that augering/overboring the holes and cinching the bolts too tight
were major contributors to the trunk cracking later. Oh and drink
a beer before you start, take your time and drink a couple more
when you are done and admiring your work. Good Luck