2016 Mazda 6 GT
Plan sounds doable. Peter from PS Sounds has a YouTube channel is probably the biggest authority on ib I know of. Watch some of his videos. You need at least half of your cone area to be cut in your vehicle. Isolate the front from the rear as close to 100% as you can. For the irregular surfaces maybe something like bondoglass to fill the voids. Tape up any metal and use a releasing agent so it’s removable. Bolt your mount securely in several spots. Be prepared for really killer subbass!!!