Can the new Duncan yoyos (12mm response/silicone sticker) actually accept flowable silicone?
No, not without modifications. I mean, you CAN use it, but it won’t last very long. The sticker recess is too shallow. Shallow and wide are not good combinations for flowable or gasket silicone. It CAN work, but it won’t last that long. The odds are that it will rip out or wear out fast.
There is a way to do it if you have some used up friction stickers lying around:
http://yoyoexpert.com/forums/index.php/topic,33629.0.html
However, I wouldn’t put anything except Duncan Sili pads in there. The reason being is that is was designed specifically with those pads in mind. The recess in other Duncans make the sili pad flush with the inner wall. On the Exit 8, the recess is slightly deeper, so that a sili pad stays slightly recessed, allowing more string to fit in the gap, and also to allow the pad recess to reduce string friction with the inner wall. Putting sili in the pad groove would probably end up being mostly flush with the wall, making the yoyo more responsive than it should be.