Hi All, Quick question. I'm trying to install/ replace the back rest and add a luggage rack to my 2005 Sportster 1200R. It currently has a short backrest. I purchased a 15in backrest and a luggage rack. After removing the existing backrest, I noticed the new one would not fit in the slot. The backrest and luggage rack where too wide. Did I just get the wrong size or I'm I going to have to change the supporting brackets..?