Ooops, looks like I posted on the wrong thread!
I meant to reply to Bob's thread on cooling. Sorry about that and thanks for not flaming me off the planet!
It strikes me, then, that baffles might be appropriate if the air inlets would allow air to bypass the cylinders completely (say, inlets much larger than the face of the cylinder(s)), or perhaps may not expose some parts of the cylinder(s) to air (say, inlets well above or below the exposed face), but should, in such a case, be "aimed" at the top and/or bottom of the cylinder(s), not directly at the middle. In cases where the air inlets are directly in front of the cylinders, and of roughly equal size, it would seem appropriate to leave them as is.
I basically followed Dick Hanson's advise on cooling a twin. The theory being that on some, not all, cowl designs most of the air flow passes straight to the exit opening rather than into the cylinder fins, so would benefit from inlet baffles.
Some manufacturers (Aeroworks) recommend baffles on their 100cc sized Extras.
As gboulton mentioned above, others (Hanger 9 35% Extra 260) have have the cylinders placed directly at the cowl intake, so don't need baffles.