2013 with shaker 500 here. Changed the speakers this morning. Polk mm6501 component in front and mm651 coax in rear. I used cruchfield's wiring adapters because they have the correct polarity. Metra's are backwards. Bought some speaker adapters from Tousley Ford. Did something different owith the tweeters in the doors. I carefully drilled out the little holes on both interior door panels right under the door lock button. I drilled a circular pattern the same size as the tweeters. I mounted the tweeters on the door's steel frame behind where I drilled out each circular pattern. You can't see any difference if you're sitting in the car. Also, I used Polk MMs because at 2.7 ohms, they're closer to the stock 2 ohms than anything else I could find.*

REAR INTALL
I was able to take off the rear deck cover without removing any interior pieces. The only thing holding the rear cover down are 2 plastic push in fasteners in front where the seat belt comes out of the rear deck. I pulled out the 2 push pins that are behind the seats on the back of the side panels. This gives you enough room to get a thin hand saw in between the cover and metal frame. You can cut the first pin on each side. I discovered I could get my hand through a round hole in the trunk directly behind where the push pins go the metal frame. I snipped the 2 push pins closest to the sail panels by putting my hand through the hole with a small pair of wire cutters. Now you can carefully lift the center of the cover up while working the ends of the cover out. I intalled the speakers. I used double stick mounting tape between the cover and the metal deck to make sure the cover doesn't move when I put Iit back on.

 

If you bought the adaptor, why bother drilling into the frame? Also, I don't trust double sided tape in the summer. I've yet to find any that holds up. You might start getting unwanted vibrations

 

Any pictures? I have a Boston Acoustics component speaker setup that has been hanging out in my garage for 5 years which I would love to put into my new Mustang... I am fairly good with wiring I just am hesitant to take panels out given the car is 3 weeks old

 

The adaptors are neaded because in the 2013 the door speakers and the housing are a single piece. Once you remove them you don't have a flat surface to mount your new speakers to. So, you have to buy the speaker mounts/ adaptors from the 2010/2011 Mustang. I put the mid in the stock position and the tweeter behind the inside door panel directly under the lock/ unlock button. Looks stock. Sounds far better.

 

Pictures would be good so we can see what you are talking about with the front tweeters. Sounds like a sweet set-up. No pun intended.

 

I look forward to seeing the pics.