First do a cheap dumb test. In no wind hoist it, sheet in tight and make sure you can pull the luff tight with a couple of inchs left in you hoist and foot. If you can't, you need to look at rerigging the boat.

I am not familiar with the 400 sq ft spin, I am familiar with the 450 Smythe chutes. The 450 is a near masthead chute The big chutes on the 6.0 are great for distance races in light air.

We learned several years ago that the big chutes do not work well in bouy races. They don't "point" high enough. Most people use Tornado, I20, or NE (Smythe 350) chutes. The Tornado and I20 are pure bouy chutes. The NE (Smythe 350) is a compromise. It works well over a wider range of wind angles than the bouy chutes.

By the way I still have a 350 I would like to find a good home for.

FYI for Rolf. These chutes are huge. The 350 would require you to sheet from the rear crossbeam on the Tornado. The 450 would require a masthead hoist, rear crossbeam sheeting, a longer pole and you steer with the chute. All the rudders do is make noise.