E30 Rollbar advice

[Dave Mulhouse <mulh0021@xxxxxxxxxx>]

I need to make the next step in track safety and purchase a rollbar for
my E30.   As my driving abilities have improved, so has my speed, and in
turn my susceptibility to 'going off' or at worst crashing.  I would
like to hear from any E30 owners that have rollbars in their E30s. What
brands are available, and are there any that I should stay away from? 
How difficult is the installation?  And, is it possible to keep the rear
seat with a 4-pt rollbar?

Thanks.

------------------------------