Ok, you can relocate the battery to the trunk fine, for whatever reason. You will want to run both the positive and the negative wire back to the engine compartment and hook them up to the places they are going now. I use 1/0 gauge welding cable for this, minimum. If you don't do this, you will have hard starting issues, most likely but, the additional cabling etc. actually adds weight to the car, rather than take it away. You are best advised to contain the battery in a sealed box, vented to outside air, for safety reasons.
2014 Premium GT, SGM, Brembo, Auto, Tech, Comfort, etc. GT500s, Steeda UCA, VMP auto tune, 100 shot on BBR tune, best et: 11.38 at 120.85
2012 GT, Candy Red, Brembo, 3.73, Tech, Comfort, etc. Procal tune, Roush upper, UMI LCAs, Steeda red bracket, GT500s, 28X10X16 Hoosier slicks, best et: 11.91 at 115.23 RIP