Hi Adam,
If you ask a NoT-So knowledgeable me about Standard #3, my friend has just bought one with 4 x 9/16 bands & 5/16 shaft with Ice Pick. Performance wise, he hasn't test it enough in the water.
Everytime I bring a target board on a dive trip almost no one but me uses it cause the temptation to hunt is just to much to resist 4 my friends.
Based on my Standard #2 with 4 x 9/16" and 5/16 shaft + Ice Pick, I can shoot accurately within 1.5 - 2" diameter target from 13 feet away, consistently. 4 bands and single hand shot.
This is a 13 feet deadly gun, in my own terms.
I just bought a Standard #4 with 4 x 5/8 bands & 3/8 shafts & Muzzle Stabilizer Wing. Managed to do only 5 shots with it cause the 5/8 bands worn me out fast, even with rest tab. Removing the shaft from the 6mm ( 1/4" ) plywood is even more tiring. I don't use new gun for hunting untill I get the hang of it shooting target board. I just discovered that Standard #1 to #3 has slimmer teak stock and #4 & #5 is at least 30% thicker teak stock to go along with the extra power and recoil. I buy thru catalog you see. This gun is like the Island Mid-Handle in size but since I hate butt-2-close-2-my-mouth mid-handle, so I choose #4 Baja. The pro swear by mid-handle and since I am not a pro and having a short hand, me stick to rear handle.
My idea is always get a gun at least 2 number up from what u currently own and you are just nice doing that. With 4 x 9/16 bands & 9/16 shaft the Standard #3 should give you 17-18 feet deadly range. This I guarantee cause I have #2 and #4 tested.
A Riffe Shooting Range Catalog will print 20 feet for #3 with 3 bands, for me I rate range very conservatively cause fish penetration is to be included. I also based my calculation on the Ice Pick spearhead and this spearhead consume more kinetic energy for penetration than a slim drag free Hawaiian shaft even at the same shaft diameter.
If I were you what I will do is to get #3 with the muzzle re-inforcement ( a must ) and use 4 x 9/16 bands. If you can swap the provided 9/16 threaded shaft with a 9/16" Hawaiian shaft, go for it. Then buy a 3/8" shafts with either a large spearhead or Ice Pick for the tuna hunting. Then if there is cash to spare buy another 9/32" Hawaiian shaft.
The #3 with a 3/8" shaft will be front heavy but should do well for tuna ( under 100 pounds ) as long you try to shoot within 17-18 feet range ( 4 bands ) , in this case a gill shot is not reccomended cause they are quite tough. Other meaty vital area shot is better. I know under 100 lbs tuna well cause I fillet enough fish many-many years ago when I catered them to restaurant. I wish I shot as many Tuna as I had filleted... he he he.
U must first test if shaft whip occurs using 4 x 9/16 bands on the #3 55 inch shaft. I will let you know when get to borrow my friend's #3 soon, for now I'm in the blind. Anyway a 9/16 Hawaiian shaft thrown by 3 bands should penetrate a decent sized fish nicely from 16 feet but logic & my experiment tells me that a barb that short can't compare to the Ice Pick deadly grip but it sure will penetrate super deep.
Now for your 9/32" shaft. Use only 2 bands with it. This light weight & thin shaft will make you wonder how such a small difference in weight and diameter can make the #3 swing & handle differently. Use this for suitable game.
I advice 3 different shaft diameter for #3 so that this one gun can serve different purposes. Buying a shaft is way cheaper than buying a gun. For my Standard #2, I have 4 different shafts : 9/32" x 50" Hawaiian, 9/16" x 50" Hawaiian , 9/16 x 48 threaded and 3/8 x 48" threaded. I just recently got those two thinner Hawaiian shafts and have not tested them.
Since there are not so many fishes in my near by waters ( unless I spend big bucks on far away trip ), I have the time shooting target board to improve my skill and my knowledge on my hardware. I really enjoy experimenting the ballistic of my spearguns.
OK, it's 21:40 PM my time Wednesday and it is ladies night in the clubs. Me need to do what a man go to do. Cheers....
Have Fun,
IYA