I'm guessing you reinforced the deck lid to make sure that spoiler doesn't rip it to pieces?

 

 

Didn't want to do any welding but mounts are sandwiched between top square pads you see here and plates underneath. Works great - top up of course when running track. There is some airflow disturbance from the rag top, but is still functional. Would like to finish off with a hard top but not spending any more scratch on this part-time track car, part-time show/daily driver. Have a purpose built M3 for the more serious stuff.