Since it's close to me I'm thinking about building a car to run in the SORC next year and above certain speeds I will have to have a cage with a seat bar. In a sedan or coupe that makes the back seat volume of the car completely useless and would relegate the vehicle to toy only status. In a wagon, though, I could still have enough practicality to drive the thing around over the summer.
As long as the rear bars catch useful parts of the floor structure, any reason a sedan roll cage wouldn't be adequate for a 2-door wagon body?
Adequate--Safety aspect is for the driver; not trying to save the shape of the vehicle.
You didn't mention what kind of car it is, but I think it will depend whether the wagon body has the same floorpan structure as a sedan - if so, the rollbar fitment should be the same.
it probably depends a lot on the type of car. A 2 door wagon makes me thing it probably shares the floorpan with a coupe version vs. the sedan.
We're talking either an Opel Kadett or Opel Ascona, and essentially they both have the same floors as their respective coupes and sedans. If anything the wagons have a bit more structure to the floor between the fenders than the regular cars.
Make sure the main hoop gives you enough room for the seat. A 2-door sounds like it might have a longer driver’s compartment than a 4-door
I quickly viewed some pictures of the BTCC Volvo 850 wagons and the cages appear to be the same as a sedan's.
There is a Datsun 510 wagon being run at the vintage group I run with and it has a sedan cage in it.
SCCA roll cage specs dictate diagonal bars from the top of the rear hop back to the rear fender wells. There is no requirement for any rollover structure rearward of the B-pillar.
Most organizations use SCCA specifications, so if you go with that you should have no problem.