If you are looking for a large diameter, but want to keep the weight down for speed, check out the Arrow Dynamic .395 Mag-XLT tapered shafts. Made up at 28″ with 70-gr CDM/Flightmate points, FlexFletch FLP 300 or Blazer X2/mini-Blazer vanes, uni-bushing and Bohning F-nock or Easton G-nock, total arrow weight should be about 254 grains, and about 290 fps. http://www.nitrostinger.com/store/store_product_detail.cfm?Product_ID=11
Tapered shafts are a bit different than parallel shafts and should not be cut from the nock end, just square up the nock end with an ASD tool, otherwise you’ll have problems finding a bushing/nock that fits. I shoot these out of my Monster 3D rig which is set at 52#/28″ and find they tune easily, have excellent FOC and very good wind drift resistence, plus the .385″ hole they punch gives a nice scoring advantage.
You can also find 50-gr, 60-gr, and 90-gr AD .395 points. I recommend using OnTarget2 SFA software for working up the arrows, FOC, length, total weight, etc.
I wouldn’t worry about spine. You aren’t going to find many ‘fat shaft’ with a spine suitable for a 50# bow without using an heavy point, which defeats its purpose for a 3D arrow. Tune for level nock travel and focus on form. JMHO
Otherwise, if proper dynamic spine is your main concern, you might check out the Carbon Express X-buster 500 or the Black Eagle Challenger 500. However, these are a heavier gpi, don’t punch quite as big a hole, and are more susceptible to wind drift.
I use the carbon express cxl pro 250 with my 29″/60# triumph. I chose them because they are light(305g), are actually spined correctly for my setup, and are large diameter for indoor 3d. They weigh 6.47g. /inch. I built them using pin nock adapters with Bohning nock, blazer shield cut 1.75″ vanes, 70g. parabolic point with a 20g. weight in them. Cxl arrows are available in 150,250 and 350 spine rating, which is hard to find in a large diameter arrow.
black z7 magnum,tommy hogg,qad,b-stingers, vaportrail: blue smoke triumph,sword,hamskae,b-stingers:desert tactical chill R, tommy hogg,limbdriver pro v,ktech, black chill x pro, limb driver pro v,sword,B-Stinger.