Specks from 12"-15" won't have any problem get'n that size Swim Shad in their mouth. Their mouths are about proportionate to a Walleye, and they're going to hit it in the Head most times anyway, to try to kill it. One of the main baits we threw at them for many-many years were H&H Cocahoes and the small Trout didn't have an issue with those...they're moderately thick-bodied baits. Out of all the 4" Skinnies that were torn-up on October 10 (that are in pans in my shop, drying off moisture as we speak, to be remelted), every one of them are SHREDDED on the Top Half or Top 2/3rd's. They nail, or Staple, that bait at the Head most of the time. I'd get that 3.5" and roll with it!