With the bar, you are required to run up to date 5 point harness. The cross bar has to be welded in, no bolt in, period. I talked to NHRA 's chief tech guy a couple of years ago about it and what he said about some magazine articles that implied they were acceptable, was not pretty! I would encourage you to weld the bar in, there is NO WAY a bolt in bar is as strong. If you decide to remove it later, you can cut through the bar at the sill plates and grind it smooth, it won't show under the carpet. Back seat access will be a PITA because of the crossbar. You have a convertible and it is flexible, hopefully you are putting in subframe connectors and they should be welded in too. I tried bolt in and they wallowed out around the bolts, this is just stamped sheetmetal, it needs welding. I was like you a few years ago, NHRA then required a bar at 11.99 and I was dipping into the 11's. I did not want to put a bar in, but I ended up doing it. It made a huge difference in structural rigidity and more than made up for the downside. You can get T-boned driving on the street just as easy as at the track. The choice is yours, But I would do it right. Just my .02. Lee.