DD Rolla

Hi everyone, umm I'm looking to lower my car abit more but before i can i need to know how much its already been lowered so i can get the springs ordered. Ive asked mechanics and they reckon they have to take out the spring to see how much its been lowered... I brought the car already lowered with 17's on it and the guy i brought it off doesnt know how much its been lowered because he didnt change suspension.. I don't want to go too low cuz it already rubs everywhere if i have people in the car or if i take hard corners, the gaurds are rolled and bashed out underneath etc etc. So i was thinking if i knew the ride height of a standard 16 twincam 88 then i could measure aprrox. how much its been lowered taking into account the larger rims. Thats how the car sits at the moment. Thanks for your help, Matt