Yes, wen you all equipment montage in your E21, it must be better 
Lay all equipment on the roof and then you mess again.
Its been better..., shure
Windows, and all others are very heavy !
I have an original one !
When you wonna the orginal differnd to your car, please wait a view days.
Wen i`m next in my garage i`m only check for you the distance.
Sorry, my personaly garage ist far from my home ! (5 km)
But one thing is the same !
Ralf has the same Car like me, even a E21 build 76 with an an 4 stroke engine.
I think his centimeters will be the same, but i dosn`t test it.
And its crasy, wenn i have a another distance.
Lay all equipment on the roof and then you mess again.
Its been better..., shure
Windows, and all others are very heavy !
I have an original one !
When you wonna the orginal differnd to your car, please wait a view days.
Wen i`m next in my garage i`m only check for you the distance.
Sorry, my personaly garage ist far from my home ! (5 km)
But one thing is the same !
Ralf has the same Car like me, even a E21 build 76 with an an 4 stroke engine.
I think his centimeters will be the same, but i dosn`t test it.
And its crasy, wenn i have a another distance.
BMW ist nicht alles, aber Spass machts trotzdem.