Challenge Roll Cage Question

I'm starting planning for my first challenge build (2020 hopeful).  One item of interest is the cage.  The car will be built with life after the challenge in mind. Namely potential NASA TT3 competition.    It looks like NASA/SCCA cage requirements overlap pretty well.  A cage built for W2W in one is legal for the other.  Where they differ wildly is to the NHRA regs.  

SCCA/NASA allow smaller main hoop and side impact tubes.  1.5" OD vs NHRA 1.75" OD.  But the W2W requires a cage vs NHRA seemingly allowing a 6pt or 4pt bar.  

What do people do for the challenge?  I don't anticipate the car would be any faster then a 12.5-13.0 second car.   The car will also be light.  Probably 1500-1700 lbs.

Do I build a W2W cage but just use NHRA size main hoop?  Do they give credit for a full cage in light cars?

Build your NASA/ SCCA cage. 

You are not going fast enough to require a cage for the NHRA. 

(Assuming it is a tin top)

For the folks that might go faster, I'm interested to hear if things have changed...

Long ago, the NHRA didn't care, and wouldn't accept a 1.5" full cage if NHRA rules required a roll bar.  1.75" or go home.  

In reply to Rodan :

NHRA has also lowered the 1/4 mile threshold when a cage is required. Roll cages are not required by the NHRA until you run 9.99. 

Only 1 Challenge car has ever run that quick.

If you need a cage, you’d better build to the NHRA

Thinking beyond Challenge cars here...  per NHRA, convertibles need a roll bar at 13.49, and other cars need a roll bar at 11.49.  

I asked this question to tom. 

If its a convertible running 13.49 or quiker, nhra regs or go home. 11.49 tin top. 

No leeway for the 1.5 tube on a convertible anymore.

Luckily the car was much slower than anticipated so i have nothing to worry about. 

In reply to Dusterbd13-michael :

Thanks!  That answers that.

According to the NHRA is a Subaru 360 a convertible or a Tin top?  It has a roof.  It will be metal.  

Also while we are on the subject what is the minimum Wheelbase for NHRA?  I am planning to stretch the car from it's stock 72" to 80" but could go a bit longer if needed.  

I've said too much....

In reply to nocones :

Here's what it says on wheelbase:

Q: My car has a shorter wheelbase than the NHRA minimum, which is 85 inches. What should I do?

A: Cars with wheelbases shorter than 85” are welcome to run at the Challenge. However, if your car exhibits gross instability during a drag pass, you may be barred from making another pass.

In terms of rollcage, I think I'd want the strongest one possible around me if I was driving a tiny Frankensteined Subaru.

In reply to nocones :

You also need to consider if you've altered the floor for nhra rules. 

In reply to nocones :

The NHRA rules on wheelbase are 85” if it has a motor swap. 

That doesn’t apply to Challenge cars (But would be relevant for post-Challenge NHRA drag racing)