All comments below assume you are building a Strafe Zon and are trying to reach a decent speed and max your physical damage. Please ignore spelling mistakes.
I have 2xShaels in my upped 170% WWS Diamond Bow to reach 95% IAS with my other equipment. 20% ammy, 20% gloves, 15% helm, and 40% bow. This reaches the "9/2 - 86% IAS" range which is fine. If I want I can throw on a belt for another 10% IAS to get the "8/2 - 105% IAS" but this is not really needed and I prefer an upped Razortail for 100% Pierce. What is needed is more damage.
So... The best thing in my opinion would be to sacrifice 5% IAS on bow for 40 more on bow damage by replacing one of the Shaels with a 40 max damage/15% IAS jewl. What this would do is keep you in the 9/2 - 86% IAS range and add a LOT of damage to your build. Possibly 200 points depending on gear and dex.
Another must would be to upgrade your bow with the cube formula to a Diamond Bow.
If you are well off then a 40/15 jewl and a Shael are the way to go. If you are using a belt without IAS. If you are using a belt with IAS then you can go ahead and put 2x40/15 jewls in your bow. But then you use a lot more points in Pierce and never reach 100%.
I personally would unsocket my bow and drop a 40/15% jewl in it if I ever found one. I would unsocket it for any xx/15% jewl since the strafe speed would be the same and I would benefit from the extra mod. second socket gets a Shael nomatter what.
Please let me know how it works out and what other equipment you are using. My Zon was supposed to be a Glass Cannon but with almost maxed resists in Hell she suvives better than most pally's and I didn't use any points in Vit

be carefull which monsters you tank tho.