This was originally a message I sent yesterday to the PCA folks here in Dallas.... I'll repeat it in "NSX form" here because it is advice that I think everyone should listen to:
The advice I see you have already gotten from others as well as your own assessment is spot on... a multi-point harness system will improve your ability to control the car effectively in two ways: 1. improve seat of the pants feel and 2. not using your appendenges, energy and attention to keep yourself in the seat in the first place.
This has been discussed at great length in this forum before... But I'll summarize my thoughts / cautions here:
1. Do not use a multi-point harness system without a full roll bar
(preferably a cage) in the car. In the event of a rollover, your upper torso has no way to "fall out" of the shoulder straps and keep the cervical region of your spine (head/neck area) from being crushed, snapped or pushed into the thoracic region. Does this sound bad? Yes. It should, because it is. Using the factory 3 point system is SAFER in a vehicle without a proper roll bar / cage.
...now, if you are still willing to undertake the risk:
2. Use a 5th (and even 6th) point / anti-sub strap. To not do this defeats the primary purpose of the harness - safety. In fact, to not do this will put you at greater (almost certain) risk for internal injury than if you had just used the factory 3 point system in a frontal crash. Wrapping the anti-sub belt around the front of the seat doesn't cut it, either. It should be situated such that female passengers look at you in the harness system and ask if the 5th/6th point causes any problems, if you know what I mean. If you're not willing to modify / cut your seat (or use a proper racing seat), rethink the harness idea.
...and if you're STILL willing to go the harness route:
3. Go with 3" SFI homologated belts manufactured in the last 2 years (instead of the less expensive 2" "tuning"-style belts). I have used the Sparco-branded belts made by TRW / Sabelt, and recommend them. In the Grand-Am Cup NSX we just finished building out, we have installed a TEAMTECH harness, and I have found the "vest" system they employ in addition to the 3" belts to be very comfortable. It is also more difficult to accidentally unlock their cam system than others (including Sparco, Simpson, etc.) Also - I would recommend "pull-UP" lap belts... the pull-down belts are a pain in the butt unless you have an F1-class pit crew to help you with them.
...still thinking about it?
4. Use a harness bar to attach the shoulder straps to. It's the proper way to make sure that in the event of a crash, the harness system stays attached to what it is mounted to. I know of people mouting the shoulder straps to the floor without a bar. I wouldn't trust it, and wouldn't do it. You can also loop the harnesses through a bar and mount them to the floor or to the seat mounting bolts directly. Would it work? Maybe, but I don't want to be the one to test that theory. Give me a properly made bar from Dali Racing.
EDR
