A question regarding shurikens and doubleshot

[threefeetunder]

So shurikens can get extra hits that are not originating from doubleshot, thanks to both shuriken expertise and ninja training (both of which give you x% chance to throw an extra shuriken, where x = your total dex), and unlike manyshot and 10k stars, they don't reduce your doubleshot.

Given the above, does this mean that each extra shot can proc yet another shuriken through doubleshot? What I mean is, imagine if you throw a shuriken. Both shuriken expertise and ninja training proc, so 3 shurikens are thrown. Assuming 100% doubleshot, would this mean you throw 6 shurikens (1 extra for all 3), or would this only affect the first one, meaning you only get 4?

[Firewall]

From the DDOWiki description: "Doubleshot grants a character a chance to make an additional attack roll with their ranged weapon any time they make a ranged attack."

Since Shuriken Expertise and Ninja Training are too both handled as another attack roll during a single ranged attack i would assume that Doubleshot is yet another check for an additional shuriken during one attack. The same is true for 10kstars (and Manyshot too) which should also not be able to proc an additional shuriken with Doubleshot. You simply have three (or four if 10kstars) different checks for an additional shuriken attack roll for every ranged attack that you make. Not tested this thoroughly though but if it is working as the description suggests it should only proc once per ranged attack and not once per shuriken attack roll. So when staying with your example you should only get 4 shuriken at max.