600 all the way. It is possible to deceive ones eyes. It happens all the time. I guess though when the results end up somewhat favorable, it is hard to argue.
A big and common mistake is the thought that adding or subtracting weight to the front of an arrow is all that it takes to go from one spine to another. While is certainly will weaken or stiffen the reaction of an arrow, it is not nearly as significant as going from one spine to another or as profound as cutting chunks of shaft.
Something you will rarely hear someone tell you when explaining bare shafting...(assuming Rh shooter) an shaft with nock kicking to the left upon release can be both too weak and too stiff... yep, I said it too stiff. A shaft with no feathers bounces off of the riser has no way to correct itself to give a kick right (stiff) showing. One must always be aware of possible false readings while tuning.
While I'm not in South Africa, I'll happily send stuff to you and with very little persuading be more than happy to bring it to ya.
I've been there a couple of times and once to Namibia. Tie up a big fat bush pig for me and I'll be right over with all kinds of goodies
BigJim is not afraid of big airplanes with very small seats and 16 hour flights but you better have plenty of biltong on hand...I'm kind of partial to the spicy giraffe. I can eat my weight in it.
BigJim