Wayne I applaud your decision to require full containment seats by all of your competitors. However most rules in racing especially safety rules come about after the majority of the racers have already adapted the idea for use by their team because they think it wise. I go back to sprints and midgets that did not even have a roll bar, someone then put a chrome hoop behind the driver and pretty soon the thickness of the tube and distance over the top of the helmet were introduced by the sanctioning bodies. Then following hard top and modified practice someone bolted a cage in place of the roll bar and these drivers were called "sissies". Pretty soon everybody was using them and the powers that be then introduced new rules for the specifications for the cages.
Seats are becoming more popular all the time but I think head and neck restraints are slightly ahead of the seats in open wheel racers right now.
In open wheel racing drivers depend on side vision to survive, it is true racers are supposed to drive to take care of the car they are overtaking at least until their front wheel is even with the cockpit of the car ahead. The younger drivers coming up now many times don't adhere to this basic etiquette of open wheel racing. That side vision interrupted by these seats might help a driver prevent contact with the overtaking car.
The seat people are starting to design open wheel seats now that will be quite different from stock car seats.
I know you don't like wings but at our speeds they sure do a lot to make our crashes less violent. Many people see wings as crutches and in fact they are. We lean on these things in the turns and they sure help the inexperienced drivers get use to racing and staying on the race track. A wing driver is no less a driver than a wingless driver. Each require different driving styles, ant the god driver can switch back and forth effortlessly.
We run 4 point crash bars instead of the lighter 3 point style nerf bar. Like Cecil said this is close to those wrap around rental bumpers. The easiest way to flip someone you have a problem with is to drop your right front wheel just in front of the other guys left rear and let off the gas a little. Crash bars won't let him do that to you, and helps prevent unwanted flips.
Sure hope your rules work out for you, but the guy that just bought a $4000.00 used car to race with you is sure going to think twice about another grand for a seat. As For you "Henchcraft" people with your $20,000.00 or $25,000.00 race car that grand is just a drop in the bucket. Keep your races on 1/4 mile and shorter tracks and stay away from Bubba's place and you got a pretty safe race program.
Honest Dad himself

