For CVR driver's education, rollbars are required in cabiolets and Boxsters, and roll cages are required in all open cars and targa's/914's without roofs. Aside from a custom designed/welded rollbar or rollcage solution, there are several sources for rollbars which fit all of our Porsche models.
The DAS SportsBar is a bolt-in (they also make a weld-only model) rollbar which sits on the body sills, as opposed to the floor or wheel well. On a 911, it takes 15-20 minutes to put it in or take it out, and it doesn't require drilling any holes or damage to your interior. It meets PCA Club Racing requirements (Note: The PCA Club Racing rollbar specs are on the PCA website under Club Racing, Club Rules), and runs $685-$900. Autopower rollbars bolt into your floor and wheel wells. If you use an Autopower rollbar (or one with similar feet), you might consider welding a piece of "L" shaped metal to the floor/sill between the rollbar feet and the floor, for added support/strength. Autopower bars are PCA Club Racing approved, and start around $250, or more if you want a removable harness or diagonal support. The removable diagonal support means you can use the rear seat area for small beings in between events. However, if you do this you'll need to ensure that the rollbar is covered in safety foam so nobody can bump their head. Safety Devices makes a sill-mounted rollbar with optional harness bar and a removable diagonal supports. It requires welding the front brackets to the sills, doesn't meet PCA Club Racing requirements and runs around $600. OG Racing makes their own rollbar which requires welding to install, meets PCA Club Racing requirements, and runs around $450. An accessory option you have, which is required in PCA Club Racing, is a seat back brace which attaches to the harness bar portion of the rollbar. You can fabricate your own, or buy one: Brey-Krause makes an adjustable model which bolts or welds to your rollbar which runs around $200. I/O Port and Autopower also make adjustable braces that bolt to your seat for around $65. Finally, you should cover any part of the rollbar with safety foam that a head/helmet might hit (regardless of whether or not you have a removable diagonal bar).
Written by Bill Gregory for the "Challenge", monthly publication of the Connecticut Valley Region, Porsche Club of America.