That's a good question. You might also try automotive type forums, particularly those that deal with modifications such as you've mentioned - possibly off-road type forum. If faced with that question I'd be calling my local dealer and would speak with the service department.
In general I'd think that mods such as you describe would not make it impossible for the air bag to deploy but the biggest concern that I'd have is creating a situation where it is too sensitive and might trigger too easily. Deployment of the air bag carries some risk of injury - the thinking being that it provides more protection, overall, in a significant collision.