I just put a Maximum Motorsports bar in my '14 over the weekend, the way the downtubes come down from the main hoop made it nearly impossible to leave the panels in without major surgery, so I left them out.
Yes, trimming the rear interior panels is a PITA. When I first read this I thought you were saying you left the downtubes themselves out, yikes!
Those tubes do need to be installed, of course, to make the bar structurally sound in a rollover and also to anchor your shoulder harnesses in a real impact.
And Maximum recommends that the rear downbars be WELDED in once they are fitted in the car. They "unbolt" simply to make this kit easier to transport flat on a pallet.
This goes for all 4-point roll bar kits - WELD THE REAR BARS FULLY TO THE MAIN HOOP or it is almost worthless.
Also, anyone doing track events using a 4-point bar should always order it with the
optional diagonal brace, shown above. Maximum will add this for $100, and it adds significant torsional rigidity to the roll bar. Its a MUST HAVE option for track use. Only drag racers would think of ordering a roll bar without this.
Last thing and I'll shut up - the gaps from the bars to the interior panels yall are showing hurt my brain. It looks like the panels were cut with a chain saw and you could drive a truck through the gap. The images above were from my car, our very first Maximum Motorsports 4-point install done 3-4 years ago. The gaps from the interior panels to the tubes are less than 1 mm wide, and we've gotten better on the last dozen installs to the point that the gaps are TIGHT.
It doesn't take special tools to manage this - just time and patience. Measure, mock-up, mark, cut the opening small, test fit, and repeat. Over and over until you sneak up on the tighter tolerances of the panel to bar fit. A roll bar install on an S197 takes us 8 hours of shop time, because it goes in and out of the car at least 4 times. First time is to mock-up the rear downbars, tack those in the car, and remove to final weld.
Then we start fitting the interior panels to the bar, where it might go in 1-2 or more times. Then it comes out again for final grinding of the newly welded junction and powder coating (or paint). Then it goes in again for the last time when it comes back from powder. Its a 3-4 day process, including the powdering coating time, so we usually schedule a car to be here for a week, and getting the bar made might take 1-4 weeks. If you don't have the patience, skills, welder, tools and such to do this install, don't short-cut it - find a qualified shop who can install your roll bar correctly and cleanly.
Adding a proper 4-point roll bar to an HPDE or autocross car is an important decision in your personal safety, and one that shouldn't be taken lightly. Don't just take what you learn on the internet (even from me) and just buy whatever "looks cool" or "easy to install". There are difference in designs that make some designs less safe than others. I won't get into the details but of all of the 4-point bars made for the S197 (and we've seen them all in person), only the Maximum Motorsports bar with a diagonal is what I will install in a car that I want to trust my life to. The fit and finish, materials, gusset bracket for the main hoop mounts, and TUBE LAYOUT are superior to any other 4-point bolt-in kit on the market.
When you get faster or get more serious (or go W2W racing), a proper roll 6- or 8-point roll cage is required, and it is even safer than a 4-point, obviously.
With the right gear on. But for a STREET car a roll CAGE can be more dangerous - because with the additional steel tubes close to your head (the upper bars from the main hoop running forward along the roof line) you are
less safe without a helmet on. So there is a place for 4-point bars (dual use cars), but they need to be designed, built and installed correctly for the maximum level of protection from a rollover, as well as to make proper anchors for shoulder harnesses. We've seen some sketchy installs and have even fixed a few. Just don't think this is an easy "DIY" install that anyone can or should do without the right experience and skills.
Good luck,