Should I overfill the Ideal implants closer to 100% capacity to prevent rippling? I'm 5.4 ft, 108 lbs, rather thin breast tissue

There are a lot of things that can factor into rippling, implant fill volume is just one of them. Overall IDEAL does have less rippling but the thickness of the tissue covering the implant has a lot to do with it also. Without examining you it is difficult to know what you can expect so it’s probably best if you discuss this with your own surgeon. Best of luck with your procedure!

The Ideal implant has internal shells and two chambers, a posterior chamber and an anterior chamber.  The posterior chamber is always filled precisely to one volume which varies depending on the overall size of the implants.  The outer or anterior chamber has a range of either "high" or "100%"  For example, with the Ideal 370 implant it can be filled to 370 which is called "high" and corresponds to a moderate profile plus implants or to 415 which is called "100%" and corresponds to a high profile implant.  The design of the implant with the internal baffles and shells limits rippling and wrinkling. In my experience, the decision to go with " high" or "100%" depends on whether a patient is better served with a moderate plus profile or a high profile look.  A high profile might be more appropriate in a woman who has had children and wants to restore some volume to the deflated upper breast but may look less natural in a woman who has never had children and has a "tighter" breast and does not want to have an implant look.  The implant can feel slightly firmer at "100%" but I have not seen any change in the structure of the side wall which is supported by the posterior chamber and baffles.  
The Ideal implant is not designed to be overfilled beyond the recommended capacity.  All implants, silicone gel included, have some ripples along the size, and whether you feel these or not has more to do with the relative thinness or thickness of your existing breast tissue. So I would go with the experience of your board certified plastic surgeon but the Ideal implant because of its structure has less rippling then a traditional saline implant.  The decision on final fill, staying within the companies recommendations and design has more to do, in my opinion with the profile that is desired in your case and does not affect the ripples.  
In multiple cases and more than a year with the Ideal implant I have not noticed any more ripples in patients filled to the "High" or lesser volume vs the "100%" or greater of the two recommended volumes.  
A somewhat long discussion but I hope this helps.

The Ideal Implants most closely resemble high pofile implants. They are structured saline implant whcih have a range of fill volumes. In general the lower fill volumes keep the implant a little softer but with a slightly higher chance of feeling (not seeing) ripples (mostly in the lower breast). This also depends on how much breast tissue "cover" you have. The less tissue the more you might feel the ripples.